2.8.1 解答

Tue, 11 Aug 2026 11:30:00 +0800

译文 · 基于 Comprehensive Rust

原文链接: https://google.github.io/comprehensive-rust/memory-management/solution.html

2.8.1 解答

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// Copyright 2023 Google LLC
// SPDX-License-Identifier: Apache-2.0
#[derive(Debug)]
enum Language {
 Rust,
 Java,
 Perl,
}

#[derive(Clone, Debug)]
struct Dependency {
 name: String,
 version_expression: String,
}

/// 软件包的表示。
#[derive(Debug)]
struct Package {
 name: String,
 version: String,
 authors: Vec<String>,
 dependencies: Vec<Dependency>,
 language: Option<Language>,
}

impl Package {
 /// 将该包表示为依赖项，供构建其他包时使用。
 fn to_dependency(&self) -> Dependency {
 Dependency {
 name: self.name.clone(),
 version_expression: self.version.clone(),
 }
 }
}

/// Package 的构建器。使用 `build()` 创建 `Package` 本身。
struct PackageBuilder(Package);

impl PackageBuilder {
 fn new(name: impl Into<String>) -> Self {
 Self(Package {
 name: name.into(),
 version: "0.1".into(),
 authors: Vec::new(),
 dependencies: Vec::new(),
 language: None,
 })
 }

 /// 设置包版本。
 fn version(mut self, version: impl Into<String>) -> Self {
 self.0.version = version.into();
 self
 }

 /// 设置包作者。
 fn authors(mut self, authors: Vec<String>) -> Self {
 self.0.authors = authors;
 self
 }

 /// 追加一个依赖项。
 fn dependency(mut self, dependency: Dependency) -> Self {
 self.0.dependencies.push(dependency);
 self
 }

 /// 设置语言。若未设置，language 默认为 None。
 fn language(mut self, language: Language) -> Self {
 self.0.language = Some(language);
 self
 }

 fn build(self) -> Package {
 self.0
 }
}

fn main() {
 let base64 = PackageBuilder::new("base64").version("0.13").build();
 dbg!(&base64);
 let log =
 PackageBuilder::new("log").version("0.4").language(Language::Rust).build();
 dbg!(&log);
 let serde = PackageBuilder::new("serde")
 .authors(vec!["djmitche".into()])
 .version(String::from("4.0"))
 .dependency(base64.to_dependency())
 .dependency(log.to_dependency())
 .build();
 dbg!(serde);
}

2.8 练习：构建器类型 on 编程那些事儿

2.8.1 解答

2.8.1 解答