Mais um blog sobre desenvolvimento de software. Zola 2024-12-13T00:00:00+00:00 https://bshn.rs/pt/categories/arquitetura/atom.xml 2024-12-13T00:00:00+00:00 2024-12-13T00:00:00+00:00 Nikita Bishonen https://bshn.rs/pt/blog/2024-12-13-rust-micro-structure/ <p>Olá! Hoje partilho os meus pensamentos sobre uma estrutura de projeto conveniente para desenvolver microsserviços em Rust. Este é o primeiro post de uma potencial série “Microsserviços em Rust”. Se conseguir terminá-la, compilarei tudo num livro completo, por isso se notares alguma imprecisão ou tiveres os teus próprios pensamentos sobre o tema - ficaria feliz se os partilhasse comigo.</p> <p>Começarei este post com uma breve introdução. Se estás confiante no teu conhecimento do sistema de pacotes e módulos do Rust, podes saltar diretamente para o <a href="https://bshn.rs/pt/blog/2024-12-13-rust-micro-structure/#sovms">conceito central</a>.</p> <h2 id="pacotes-crates-e-modulos-em-rust"><a class="zola-anchor" href="#pacotes-crates-e-modulos-em-rust" aria-label="Anchor link for: pacotes-crates-e-modulos-em-rust"><i class="icon"></i></a> Pacotes, Crates e Módulos em Rust</h2> <blockquote> <p>Se não estás familiarizado com Rust, recomendo estudar a fonte original - o capítulo <a rel="external" href="https://doc.rust-lang.org/book/ch07-00-managing-growing-projects-with-packages-crates-and-modules.html">Managing Growing Projects with Packages, Crates and Module</a> na documentação oficial do Rust. O que se segue é a minha interpretação, que pode ser imprecisa ou incompleta.</p> </blockquote> <p>Portanto, em projetos Rust temos:</p> <ul> <li>Um Pacote contendo: <ul> <li><code>Cargo(.toml | .lock)</code></li> <li>Um ou muitos crates, cada um tendo: <ul> <li>Uma raiz do crate - <code>src/(lib.rs | main.rs | bin/*.rs)</code></li> <li>Módulos <ul> <li>inline - <code>mod _nome_ { _corpo }</code></li> <li>como ficheiros separados - <code>mod _nome_;</code> + <code>src/(_nome_.rs | _nome_/mod.rs)</code></li> </ul> </li> </ul> </li> </ul> </li> </ul> <p>Isto cria uma matrioska ou o conto de Koschei, o Imortal - a agulha (módulo) num ovo, o ovo (crate) numa galinha, a galinha (pacote) num baú (projeto).</p> <p><img src="/images/2024_12_13_rust_micro_structure_01.png" alt="Pacotes em Rust" loading="lazy" decoding="async" /></p> <p>Vamos examinar as regras de acesso aos módulos.</p> <ol> <li>Os módulos podem ser privados (ocultos) e públicos. <ol> <li>Por defeito, os módulos são privados.</li> </ol> </li> <li>As entidades dentro de um módulo também podem ser privadas e públicas. <ol> <li>Por defeito, as entidades são privadas.</li> </ol> </li> <li>E então começam interações e combinações interessantes, que proponho examinar com exemplos de código.</li> </ol> <pre class="giallo" style="color-scheme: light dark; color: light-dark(#C6D0F5, #565869); background-color: light-dark(#303446, #FAFBFC);"><code data-lang="rust"><span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">mod</span><span style="color: light-dark(#EF9F76, #565869);"> parent</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> children_private</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> pub</span><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> pub</span><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> children_public</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> pub</span><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> grandchildren</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> pub</span><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">mod</span><span style="color: light-dark(#EF9F76, #565869);"> neighbour</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span></code></pre> <p>Visualmente, a estrutura parece-se com isto:</p> <p><img src="/images/2024_12_13_rust_micro_structure_02.png" alt="Estrutura" loading="lazy" decoding="async" /></p> <p>Com este exemplo, quero mostrar as possíveis conexões entre módulos e entidades (neste exemplo, limitamo-nos a structs vazios).</p> <p>Vamos dividir isto em várias situações, que distinguiremos pelo lado que faz a chamada.</p> <h3 id=""><a class="zola-anchor" href="#" aria-label="Anchor link for: "><i class="icon"></i></a> O Que Pode um Módulo Pai Aceder?</h3> <pre class="giallo" style="color-scheme: light dark; color: light-dark(#C6D0F5, #565869); background-color: light-dark(#303446, #FAFBFC);"><code data-lang="rust"><span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">fn</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> test_visibility</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> children_private::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#E5C890, #565869);"> children_private</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> children_public::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#E5C890, #565869);"> children_public</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> children_public::grandchildren::Private; // Falha devido à privacidade do módulo.</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> children_public::grandchildren::Public; // Falha devido à privacidade do módulo.</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span></code></pre> <p>Acima, mostro um excerto de teste para o módulo pai. Como podemos ver, o acesso está disponível a ambos os módulos filhos (privado e público), mas apenas às structs públicas. O acesso aos “netos” privados e às suas structs públicas não está disponível. Visualmente, isto parece-se com:</p> <p><img src="/images/2024_12_13_rust_micro_structure_03.png" alt="Pai" loading="lazy" decoding="async" /></p> <h3 id="-1"><a class="zola-anchor" href="#-1" aria-label="Anchor link for: -1"><i class="icon"></i></a> O Que Pode um Módulo Filho Aceder?</h3> <p>Para isso, faremos uma adição e adicionaremos duas structs ao módulo pai, análogas aos filhos.</p> <pre class="giallo" style="color-scheme: light dark; color: light-dark(#C6D0F5, #565869); background-color: light-dark(#303446, #FAFBFC);"><code data-lang="rust"><span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">///</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> Testar visibilidade do modelo super e de outros sub-modelos do módulo um nível acima.</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">fn</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> test_visibility</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> super::children_private::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">children_private</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> self::grandchildren::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#E78284, #2DAE58);"> self</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">grandchildren</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span></code></pre> <p><img src="/images/2024_12_13_rust_micro_structure_04.png" alt="Filho" loading="lazy" decoding="async" /></p> <p>Como podemos ver, os tentáculos do nosso filho alcançam bastante longe, e apenas as structs privadas de módulos irmãos e filhos são inacessíveis. No entanto, as structs privadas do módulo pai estão bem ao alcance.</p> <h3 id="-2"><a class="zola-anchor" href="#-2" aria-label="Anchor link for: -2"><i class="icon"></i></a> O Que Pode um Bisneto Aceder?</h3> <pre class="giallo" style="color-scheme: light dark; color: light-dark(#C6D0F5, #565869); background-color: light-dark(#303446, #FAFBFC);"><code data-lang="rust"><span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">///</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> Testar visibilidade do modelo super e de outros sub-modelos do módulo dois níveis acima.</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">fn</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> test_visibility</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> super::super::children_private::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#CA9EE6, #F767BB);">super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">children_private</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#CA9EE6, #F767BB);">super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#CA9EE6, #F767BB);">super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span></code></pre> <p><img src="/images/2024_12_13_rust_micro_structure_05.png" alt="Bisneto" loading="lazy" decoding="async" /></p> <p>Para o bisneto, a situação é semelhante. Decidi mostrá-lo para uma melhor compreensão de como este mecanismo multinível funciona em Rust.</p> <h3 id="-3"><a class="zola-anchor" href="#-3" aria-label="Anchor link for: -3"><i class="icon"></i></a> O Que Pode um Vizinho Aceder?</h3> <blockquote> <p>Infelizmente, só reparei nesta fase que todos os diagramas até agora incluíam o vizinho dentro do módulo pai. Na realidade, está localizado ao lado, não dentro do pai. O diagrama abaixo contém a colocação correta deste módulo.</p> </blockquote> <pre class="giallo" style="color-scheme: light dark; color: light-dark(#C6D0F5, #565869); background-color: light-dark(#303446, #FAFBFC);"><code data-lang="rust"><span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">///</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> Testar visibilidade de sub-módulos dentro de outro módulo no mesmo nível.</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">fn</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> test_visibility</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> crate</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">parent</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::children_private::Private; // Falha devido à privacidade do módulo</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::children_private::Public; // Falha devido à privacidade do módulo</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::children_public::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> crate</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">parent</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">children_public</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::children_public::grandchildren::Private; // Falha devido à privacidade de um módulo</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::children_public::grandchildren::Public; // Falha devido à privacidade de um módulo</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span></code></pre> <p><img src="/images/2024_12_13_rust_micro_structure_06.png" alt="Vizinho" loading="lazy" decoding="async" /></p> <p>A situação do vizinho é bastante aborrecida - apenas entidades públicas e caminhos para elas são acessíveis. Note que o módulo pai não é público, ainda assim o vizinho consegue vê-lo 👀</p> <h2 id="sovms"><a class="zola-anchor" href="#sovms" aria-label="Anchor link for: sovms"><i class="icon"></i></a> SOVMS</h2> <p>Ou Estrutura Baseada na Visibilidade dos Módulos. A ideia é que em Rust, já temos regras de acesso definidas (que descrevi em detalhe acima) às entidades dos módulos dependendo das suas relações (que relação o módulo que faz a chamada tem com o módulo chamado).</p> <blockquote> <p>Decidi que a estrutura do projeto também deveria ser organizada com base nestas características da linguagem Rust para ser mais idiomática. A ideia é nova, e à medida que a testar, atualizarei este post.</p> </blockquote> <p>Para obter uma estrutura de projeto idiomática, devemos colocar os módulos com base em quem e o que os deve ver. Esta parte do código é usada em todo o serviço? Mova-a o mais alto possível. Outra parte do código é específica? Isole-a num ramo separado ou esconda-a mais profundamente.</p> <p>O ponto é que os módulos não devem ser decompostos de acordo com os domínios de negócio (pelo menos isto não deve ser a base da divisão). Afinal, na arquitetura de microsserviços, estes devem ser serviços separados (ou pacotes Rust separados para aplicações monolíticas). Desta forma, aspiramos à cobiçada proporção áurea de <a rel="external" href="https://en.wikipedia.org/wiki/Larry_Constantine#Structured_design">fraco acoplamento e alta coesão</a>.</p> <h3 id="-4"><a class="zola-anchor" href="#-4" aria-label="Anchor link for: -4"><i class="icon"></i></a> TL;DR</h3> <p>Como vejo a utilização desta abordagem na escrita de microsserviços? Deixe-me não perder mais do seu tempo a ler os meus pensamentos e mostrar-lhe um modelo:</p> <pre class="giallo" style="color-scheme: light dark; color: light-dark(#C6D0F5, #565869); background-color: light-dark(#303446, #FAFBFC);"><code data-lang="rust"><span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">//</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">! Este é o crate base do serviço. Melhor torná-lo uma biblioteca, para que a funcionalidade</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">//</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">! sobre como exatamente executá-lo seja armazenada separadamente dentro de um main.rs ou diferentes bins.</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">mod</span><span style="color: light-dark(#EF9F76, #565869);"> interfaces</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">!</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> graphql</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">!</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> http</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">!</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> grpc</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">!</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">mod</span><span style="color: light-dark(#EF9F76, #565869);"> core</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">!</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> api</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">!</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> config</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">!</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">mod</span><span style="color: light-dark(#EF9F76, #565869);"> resources</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">!</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> db</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">!</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> kafka</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">!</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> third_party_integration</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">!</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span></code></pre> <p>Podes criar um novo pacote com dois crates:</p> <ul> <li>main é responsável apenas por iniciar a aplicação</li> <li>lib armazena a estrutura e é usado em main, testes (integração), e “bins” adicionais se necessário</li> </ul> <h3 id="-5"><a class="zola-anchor" href="#-5" aria-label="Anchor link for: -5"><i class="icon"></i></a> Exemplo Real</h3> <p>Neste exemplo, alguns nomes foram alterados, mas esta é uma estrutura real de um de vários serviços. Escrevê-los na verdade levou-me a derivar alguma teoria geral sobre a estruturação de microsserviços em Rust.</p> <pre class="giallo" style="color-scheme: light dark; color: light-dark(#C6D0F5, #565869); background-color: light-dark(#303446, #FAFBFC);"><code data-lang="shellscript"><span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">src</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> bin</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">│</span><span style="color: light-dark(#A6D189, #CF9C00);"> └──</span><span style="color: light-dark(#A6D189, #CF9C00);"> events_processor.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> core</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">│</span><span style="color: light-dark(#A6D189, #CF9C00);"> ├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> api.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">│</span><span style="color: light-dark(#A6D189, #CF9C00);"> ├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> configuration.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">│</span><span style="color: light-dark(#A6D189, #CF9C00);"> └──</span><span style="color: light-dark(#A6D189, #CF9C00);"> mod.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> interfaces</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">│</span><span style="color: light-dark(#A6D189, #CF9C00);"> ├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> graphql</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">│</span><span style="color: light-dark(#A6D189, #CF9C00);"> │</span><span style="color: light-dark(#A6D189, #CF9C00);"> ├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> mod.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">│</span><span style="color: light-dark(#A6D189, #CF9C00);"> │</span><span style="color: light-dark(#A6D189, #CF9C00);"> ├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> mutations.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">│</span><span style="color: light-dark(#A6D189, #CF9C00);"> │</span><span style="color: light-dark(#A6D189, #CF9C00);"> ├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> queries.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">│</span><span style="color: light-dark(#A6D189, #CF9C00);"> │</span><span style="color: light-dark(#A6D189, #CF9C00);"> └──</span><span style="color: light-dark(#A6D189, #CF9C00);"> subscriptions.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">│</span><span style="color: light-dark(#A6D189, #CF9C00);"> └──</span><span style="color: light-dark(#A6D189, #CF9C00);"> mod.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> lib.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> main.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">└──</span><span style="color: light-dark(#A6D189, #CF9C00);"> resources</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> ├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> node_proxy.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> ├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> indexer_proxy.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> ├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> db.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> ├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> mod.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> ├──</span><span style="color: light-dark(#A6D189, #CF9C00);"> reservoir_proxy.rs</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> └──</span><span style="color: light-dark(#A6D189, #CF9C00);"> real_time_data_ws.rs</span></span></code></pre><h3 id="-6"><a class="zola-anchor" href="#-6" aria-label="Anchor link for: -6"><i class="icon"></i></a> A Minha Experiência</h3> <p>Posso dizer que acho esta estrutura conveniente porque combina as vantagens das antigas arquiteturas de três camadas e das arquiteturas hexagonais aplicáveis a microsserviços. Dividimos a nossa aplicação em três ramos:</p> <ol> <li><code>Resources</code> - tudo o que está fora do nosso serviço e onde somos consumidores vai aqui. Bases de dados, outros serviços, message brokers (parcialmente). Tudo onde iniciamos a comunicação e onde sabemos mais sobre o interlocutor do que eles sabem sobre nós. (Anteriormente chamava esta parte <code>clients</code>, mas o nome resources parece mais apropriado agora). A tarefa principal dos resources é lidar com as especificidades da interação com estes recursos. Aqui podemos ter implementações de traits para codificar e descodificar os nossos tipos de dados para uma base de dados específica, e aqui escrevemos “proxies” que transformam esquemas de outros serviços no que operamos dentro do serviço.</li> <li><code>Interfaces</code> - tudo o que serve como pontos de entrada para pedidos ao nosso serviço vai aqui. API HTTP/gRPC, GraphQL, até message brokers se fizerem parte do processamento de pedidos recebidos - tudo vai aqui. Tal como os resources, aqui tentamos isolar todas as especificidades relacionadas com o mecanismo particular de interação cliente-servidor (é por isso que anteriormente chamava esta parte <code>servers</code>). Por exemplo, todas as deserializações de pedidos e serializações de respostas devem ser implementadas aqui. Depois disso, devemos trabalhar com tipos “limpos”.</li> <li><code>Core</code> - este é o lugar “mais limpo” e “mais importante” no nosso serviço. A lógica de negócio principal é implementada aqui. Aqui operamos não com JSON que veio pela rede, mas com a sua representação estaticamente tipada e verificada. A partir do core, podemos chamar resources, mas idealmente não devemos saber nada sobre interfaces. No entanto, não devemos ter acesso a conceitos de baixo nível dos resources. Apenas à API pública.</li> </ol> <p>Como é que a colocação de módulos ajuda aqui? Vemos que todos os três ramos são vizinhos entre si, o que significa que só podem conhecer coisas públicas, e as especificidades são seguras para mudar (por exemplo, mudar a base de dados ou suportar REST junto com gRPC).</p> <p>Dentro dos ramos, vamos do geral para o específico e também separamos partes independentes em ramos.</p> <p><code>graphql</code> consiste em <code>queries</code>, <code>mutations</code>, <code>subscriptions</code> independentes, mas o esquema comum está no módulo raiz:</p> <pre class="giallo" style="color-scheme: light dark; color: light-dark(#C6D0F5, #565869); background-color: light-dark(#303446, #FAFBFC);"><code data-lang="rust"><span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">//</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;">! graphql/mod.rs</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">pub</span><span style="color: light-dark(#CA9EE6, #F767BB);"> async</span><span style="color: light-dark(#CA9EE6, #F767BB);"> fn</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> schema</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#81C8BE, #ADB1C2);"> -&gt;</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;"> Result</span><span style="color: light-dark(#99D1DB, #ADB1C2);">&lt;</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Schema</span><span style="color: light-dark(#99D1DB, #ADB1C2);">&lt;</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Query</span><span style="color: light-dark(#949CBB, #ADB1C2);">,</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;"> Mutation</span><span style="color: light-dark(#949CBB, #ADB1C2);">,</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;"> Subscription</span><span style="color: light-dark(#99D1DB, #ADB1C2);">&gt;</span><span style="color: light-dark(#99D1DB, #ADB1C2);">&gt;</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> let</span><span> configuration</span><span style="color: light-dark(#81C8BE, #ADB1C2);"> =</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;"> Configuration</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">from_env</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#81C8BE, #ADB1C2);">?</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> let</span><span> pool</span><span style="color: light-dark(#81C8BE, #ADB1C2);"> =</span><span style="color: light-dark(#E5C890, #565869);"> database</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">connect</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#81C8BE, #ADB1C2);">&amp;</span><span>configuration</span><span style="color: light-dark(#81C8BE, #ADB1C2);">.</span><span style="color: light-dark(#8CAAEE, #565869);">database</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#81C8BE, #ADB1C2);">.</span><span style="color: light-dark(#CA9EE6, #F767BB);">await</span><span style="color: light-dark(#81C8BE, #ADB1C2);">?</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> let</span><span> producer</span><span style="color: light-dark(#81C8BE, #ADB1C2);"> =</span><span style="color: light-dark(#E5C890, #565869);"> kafka</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">build_producer</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#81C8BE, #ADB1C2);">&amp;</span><span>configuration</span><span style="color: light-dark(#81C8BE, #ADB1C2);">.</span><span style="color: light-dark(#8CAAEE, #565869);">kafka</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#81C8BE, #ADB1C2);">?</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Ok</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Schema</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">build</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Query</span><span style="color: light-dark(#949CBB, #ADB1C2);">,</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;"> Mutation</span><span style="color: light-dark(#949CBB, #ADB1C2);">,</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;"> Subscription</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span></span> <span class="giallo-l"><span style="color: light-dark(#81C8BE, #ADB1C2);"> .</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">enable_federation</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span></span> <span class="giallo-l"><span style="color: light-dark(#81C8BE, #ADB1C2);"> .</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;">enable_subscription_in_federation</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span></span> <span class="giallo-l"><span style="color: light-dark(#81C8BE, #ADB1C2);">...</span></span></code></pre> <p>Cada sub-módulo chamará métodos públicos “limpos” de <code>core/api.rs</code>.</p> <p><code>api.rs</code> no meu exemplo contém tipos comuns na raiz (tanto privados como públicos), aos quais os seus sub-módulos <code>api::queries</code> e <code>api::commands</code> têm acesso total, mas tipos privados e implementações do próprio módulo <code>api</code> são inacessíveis a qualquer pessoa exceto aos seus sub-módulos.</p> <h2 id="-7"><a class="zola-anchor" href="#-7" aria-label="Anchor link for: -7"><i class="icon"></i></a> Materiais Adicionais</h2> <p>Se estás interessado em “brincar” com o exemplo deste artigo, aqui está o código completo do projeto do capítulo de módulos:</p> <pre class="giallo" style="color-scheme: light dark; color: light-dark(#C6D0F5, #565869); background-color: light-dark(#303446, #FAFBFC);"><code data-lang="rust"><span class="giallo-l"><span style="color: light-dark(#E5C890, #ADB1C2);font-style: italic;">#</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;">!</span><span style="color: light-dark(#949CBB, #ADB1C2);">[</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;">allow</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;">clippy</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;">all</span><span style="color: light-dark(#949CBB, #ADB1C2);">,</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> dead_code</span><span style="color: light-dark(#949CBB, #ADB1C2);">,</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> path_statements</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#949CBB, #ADB1C2);">]</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">fn</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> main</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> println!</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#A6D189, #ADB1C2);">&quot;</span><span style="color: light-dark(#A6D189, #CF9C00);">Hello, modules privacy!</span><span style="color: light-dark(#A6D189, #ADB1C2);">&quot;</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">mod</span><span style="color: light-dark(#EF9F76, #565869);"> parent</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> pub</span><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> children_private</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> pub</span><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> pub</span><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> children_public</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> pub</span><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> mod</span><span style="color: light-dark(#EF9F76, #565869);"> grandchildren</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> pub</span><span style="color: light-dark(#CA9EE6, #F767BB);"> struct</span><span style="color: light-dark(#E5C890, #565869);font-style: italic;"> Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> ///</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> Testar visibilidade do modelo super e de outros sub-modelos do módulo dois níveis acima.</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> fn</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> test_visibility</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> super::super::children_private::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#CA9EE6, #F767BB);">super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">children_private</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#CA9EE6, #F767BB);">super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#CA9EE6, #F767BB);">super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> ///</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> Testar visibilidade do modelo super e de outros sub-modelos do módulo um nível acima.</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> fn</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> test_visibility</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Private</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> super::children_private::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> super</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">children_private</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> self::grandchildren::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#E78284, #2DAE58);"> self</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">grandchildren</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> ///</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> Testar visibilidade de sub-módulos dentro do módulo atual.</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> fn</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> test_visibility</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> children_private::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#E5C890, #565869);"> children_private</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> children_public::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#E5C890, #565869);"> children_public</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> children_public::grandchildren::Private; // Falha devido à privacidade do módulo.</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> children_public::grandchildren::Public; // Falha devido à privacidade do módulo.</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);">mod</span><span style="color: light-dark(#EF9F76, #565869);"> neighbour</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> ///</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> Testar visibilidade de sub-módulos dentro de outro módulo no mesmo nível.</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> fn</span><span style="color: light-dark(#8CAAEE, #09A1ED);font-style: italic;"> test_visibility</span><span style="color: light-dark(#949CBB, #ADB1C2);">(</span><span style="color: light-dark(#949CBB, #ADB1C2);">)</span><span style="color: light-dark(#949CBB, #ADB1C2);"> {</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> crate</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">parent</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::children_private::Private; // Falha devido à privacidade do módulo</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::children_private::Public; // Falha devido à privacidade do módulo</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::children_public::Private; // Falha devido à privacidade da struct</span></span> <span class="giallo-l"><span style="color: light-dark(#CA9EE6, #F767BB);"> crate</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">parent</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #565869);">children_public</span><span style="color: light-dark(#81C8BE, #ADB1C2);">::</span><span style="color: light-dark(#E5C890, #13BBB7);font-style: italic;">Public</span><span style="color: light-dark(#949CBB, #ADB1C2);">;</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::children_public::grandchildren::Private; // Falha devido à privacidade de um módulo</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> //</span><span style="color: light-dark(#949CBB, #ADB1C2);font-style: italic;"> crate::parent::children_public::grandchildren::Public; // Falha devido à privacidade de um módulo</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);"> }</span></span> <span class="giallo-l"><span style="color: light-dark(#949CBB, #ADB1C2);">}</span></span></code></pre>