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500 lines
13 KiB
Markdown
500 lines
13 KiB
Markdown
---
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name: rust-patterns
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description: 地道的Rust模式、所有权、错误处理、特质、并发，以及构建安全、高性能应用程序的最佳实践。
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origin: ECC
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---
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# Rust 开发模式
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构建安全、高性能且可维护应用程序的惯用 Rust 模式和最佳实践。
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## 何时使用
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* 编写新的 Rust 代码时
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* 评审 Rust 代码时
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* 重构现有 Rust 代码时
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* 设计 crate 结构和模块布局时
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## 工作原理
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此技能在六个关键领域强制执行惯用的 Rust 约定：所有权和借用，用于在编译时防止数据竞争；`Result`/`?` 错误传播，库使用 `thiserror` 而应用程序使用 `anyhow`；枚举和穷尽模式匹配，使非法状态无法表示；用于零成本抽象的 trait 和泛型；通过 `Arc<Mutex<T>>`、通道和 async/await 实现的安全并发；以及按领域组织的最小化 `pub` 接口。
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## 核心原则
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### 1. 所有权和借用
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Rust 的所有权系统在编译时防止数据竞争和内存错误。
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```rust
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// Good: Pass references when you don't need ownership
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fn process(data: &[u8]) -> usize {
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data.len()
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}
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// Good: Take ownership only when you need to store or consume
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fn store(data: Vec<u8>) -> Record {
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Record { payload: data }
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}
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// Bad: Cloning unnecessarily to avoid borrow checker
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fn process_bad(data: &Vec<u8>) -> usize {
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let cloned = data.clone(); // Wasteful — just borrow
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cloned.len()
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}
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```
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### 使用 `Cow` 实现灵活的所有权
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```rust
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use std::borrow::Cow;
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fn normalize(input: &str) -> Cow<'_, str> {
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if input.contains(' ') {
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Cow::Owned(input.replace(' ', "_"))
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} else {
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Cow::Borrowed(input) // Zero-cost when no mutation needed
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}
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}
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```
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## 错误处理
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### 使用 `Result` 和 `?` —— 切勿在生产环境中使用 `unwrap()`
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```rust
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// Good: Propagate errors with context
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use anyhow::{Context, Result};
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fn load_config(path: &str) -> Result<Config> {
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let content = std::fs::read_to_string(path)
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.with_context(|| format!("failed to read config from {path}"))?;
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let config: Config = toml::from_str(&content)
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.with_context(|| format!("failed to parse config from {path}"))?;
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Ok(config)
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}
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// Bad: Panics on error
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fn load_config_bad(path: &str) -> Config {
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let content = std::fs::read_to_string(path).unwrap(); // Panics!
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toml::from_str(&content).unwrap()
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}
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```
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### 库错误使用 `thiserror`，应用程序错误使用 `anyhow`
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```rust
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// Library code: structured, typed errors
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use thiserror::Error;
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#[derive(Debug, Error)]
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pub enum StorageError {
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#[error("record not found: {id}")]
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NotFound { id: String },
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#[error("connection failed")]
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Connection(#[from] std::io::Error),
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#[error("invalid data: {0}")]
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InvalidData(String),
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}
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// Application code: flexible error handling
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use anyhow::{bail, Result};
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fn run() -> Result<()> {
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let config = load_config("app.toml")?;
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if config.workers == 0 {
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bail!("worker count must be > 0");
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}
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Ok(())
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}
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```
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### 优先使用 `Option` 组合子而非嵌套匹配
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```rust
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// Good: Combinator chain
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fn find_user_email(users: &[User], id: u64) -> Option<String> {
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users.iter()
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.find(|u| u.id == id)
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.map(|u| u.email.clone())
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}
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// Bad: Deeply nested matching
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fn find_user_email_bad(users: &[User], id: u64) -> Option<String> {
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match users.iter().find(|u| u.id == id) {
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Some(user) => match &user.email {
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email => Some(email.clone()),
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},
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None => None,
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}
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}
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```
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## 枚举和模式匹配
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### 将状态建模为枚举
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```rust
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// Good: Impossible states are unrepresentable
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enum ConnectionState {
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Disconnected,
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Connecting { attempt: u32 },
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Connected { session_id: String },
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Failed { reason: String, retries: u32 },
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}
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fn handle(state: &ConnectionState) {
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match state {
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ConnectionState::Disconnected => connect(),
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ConnectionState::Connecting { attempt } if *attempt > 3 => abort(),
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ConnectionState::Connecting { .. } => wait(),
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ConnectionState::Connected { session_id } => use_session(session_id),
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ConnectionState::Failed { retries, .. } if *retries < 5 => retry(),
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ConnectionState::Failed { reason, .. } => log_failure(reason),
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}
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}
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```
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### 穷尽匹配 —— 业务逻辑中不使用通配符
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```rust
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// Good: Handle every variant explicitly
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match command {
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Command::Start => start_service(),
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Command::Stop => stop_service(),
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Command::Restart => restart_service(),
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// Adding a new variant forces handling here
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}
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// Bad: Wildcard hides new variants
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match command {
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Command::Start => start_service(),
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_ => {} // Silently ignores Stop, Restart, and future variants
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}
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```
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## Trait 和泛型
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### 接受泛型，返回具体类型
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```rust
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// Good: Generic input, concrete output
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fn read_all(reader: &mut impl Read) -> std::io::Result<Vec<u8>> {
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let mut buf = Vec::new();
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reader.read_to_end(&mut buf)?;
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Ok(buf)
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}
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// Good: Trait bounds for multiple constraints
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fn process<T: Display + Send + 'static>(item: T) -> String {
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format!("processed: {item}")
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}
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```
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### 使用 Trait 对象进行动态分发
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```rust
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// Use when you need heterogeneous collections or plugin systems
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trait Handler: Send + Sync {
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fn handle(&self, request: &Request) -> Response;
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}
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struct Router {
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handlers: Vec<Box<dyn Handler>>,
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}
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// Use generics when you need performance (monomorphization)
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fn fast_process<H: Handler>(handler: &H, request: &Request) -> Response {
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handler.handle(request)
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}
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```
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### 使用 Newtype 模式确保类型安全
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```rust
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// Good: Distinct types prevent mixing up arguments
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struct UserId(u64);
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struct OrderId(u64);
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fn get_order(user: UserId, order: OrderId) -> Result<Order> {
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// Can't accidentally swap user and order IDs
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todo!()
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}
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// Bad: Easy to swap arguments
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fn get_order_bad(user_id: u64, order_id: u64) -> Result<Order> {
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todo!()
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}
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```
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## 结构体和数据建模
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### 使用构建器模式进行复杂构造
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```rust
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struct ServerConfig {
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host: String,
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port: u16,
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max_connections: usize,
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}
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impl ServerConfig {
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fn builder(host: impl Into<String>, port: u16) -> ServerConfigBuilder {
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ServerConfigBuilder { host: host.into(), port, max_connections: 100 }
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}
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}
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struct ServerConfigBuilder { host: String, port: u16, max_connections: usize }
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impl ServerConfigBuilder {
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fn max_connections(mut self, n: usize) -> Self { self.max_connections = n; self }
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fn build(self) -> ServerConfig {
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ServerConfig { host: self.host, port: self.port, max_connections: self.max_connections }
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}
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}
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// Usage: ServerConfig::builder("localhost", 8080).max_connections(200).build()
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```
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## 迭代器和闭包
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### 优先使用迭代器链而非手动循环
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```rust
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// Good: Declarative, lazy, composable
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let active_emails: Vec<String> = users.iter()
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.filter(|u| u.is_active)
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.map(|u| u.email.clone())
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.collect();
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// Bad: Imperative accumulation
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let mut active_emails = Vec::new();
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for user in &users {
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if user.is_active {
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active_emails.push(user.email.clone());
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}
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}
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```
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### 使用带有类型注解的 `collect()`
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```rust
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// Collect into different types
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let names: Vec<_> = items.iter().map(|i| &i.name).collect();
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let lookup: HashMap<_, _> = items.iter().map(|i| (i.id, i)).collect();
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let combined: String = parts.iter().copied().collect();
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// Collect Results — short-circuits on first error
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let parsed: Result<Vec<i32>, _> = strings.iter().map(|s| s.parse()).collect();
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```
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## 并发
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### 使用 `Arc<Mutex<T>>` 处理共享可变状态
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```rust
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use std::sync::{Arc, Mutex};
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let counter = Arc::new(Mutex::new(0));
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let handles: Vec<_> = (0..10).map(|_| {
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let counter = Arc::clone(&counter);
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std::thread::spawn(move || {
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let mut num = counter.lock().expect("mutex poisoned");
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*num += 1;
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})
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}).collect();
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for handle in handles {
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handle.join().expect("worker thread panicked");
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}
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```
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### 使用通道进行消息传递
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```rust
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use std::sync::mpsc;
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let (tx, rx) = mpsc::sync_channel(16); // Bounded channel with backpressure
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for i in 0..5 {
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let tx = tx.clone();
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std::thread::spawn(move || {
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tx.send(format!("message {i}")).expect("receiver disconnected");
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});
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}
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drop(tx); // Close sender so rx iterator terminates
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for msg in rx {
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println!("{msg}");
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}
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```
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### 使用 Tokio 进行异步编程
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```rust
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use tokio::time::Duration;
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async fn fetch_with_timeout(url: &str) -> Result<String> {
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let response = tokio::time::timeout(
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Duration::from_secs(5),
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reqwest::get(url),
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)
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.await
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.context("request timed out")?
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.context("request failed")?;
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response.text().await.context("failed to read body")
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}
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// Spawn concurrent tasks
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async fn fetch_all(urls: Vec<String>) -> Vec<Result<String>> {
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let handles: Vec<_> = urls.into_iter()
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.map(|url| tokio::spawn(async move {
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fetch_with_timeout(&url).await
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}))
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.collect();
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let mut results = Vec::with_capacity(handles.len());
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for handle in handles {
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results.push(handle.await.unwrap_or_else(|e| panic!("spawned task panicked: {e}")));
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}
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results
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}
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```
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## 不安全代码
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### 何时可以使用 Unsafe
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```rust
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// Acceptable: FFI boundary with documented invariants (Rust 2024+)
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/// # Safety
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/// `ptr` must be a valid, aligned pointer to an initialized `Widget`.
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unsafe fn widget_from_raw<'a>(ptr: *const Widget) -> &'a Widget {
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// SAFETY: caller guarantees ptr is valid and aligned
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unsafe { &*ptr }
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}
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// Acceptable: Performance-critical path with proof of correctness
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// SAFETY: index is always < len due to the loop bound
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unsafe { slice.get_unchecked(index) }
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```
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### 何时不可以使用 Unsafe
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```rust
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// Bad: Using unsafe to bypass borrow checker
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// Bad: Using unsafe for convenience
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// Bad: Using unsafe without a Safety comment
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// Bad: Transmuting between unrelated types
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```
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## 模块系统和 Crate 结构
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### 按领域组织，而非按类型
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```text
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my_app/
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├── src/
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│ ├── main.rs
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│ ├── lib.rs
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│ ├── auth/ # 领域模块
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│ │ ├── mod.rs
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│ │ ├── token.rs
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│ │ └── middleware.rs
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│ ├── orders/ # 领域模块
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│ │ ├── mod.rs
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│ │ ├── model.rs
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│ │ └── service.rs
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│ └── db/ # 基础设施
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│ ├── mod.rs
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│ └── pool.rs
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├── tests/ # 集成测试
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├── benches/ # 基准测试
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└── Cargo.toml
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```
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### 可见性 —— 最小化暴露
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```rust
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// Good: pub(crate) for internal sharing
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pub(crate) fn validate_input(input: &str) -> bool {
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!input.is_empty()
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}
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// Good: Re-export public API from lib.rs
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pub mod auth;
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pub use auth::AuthMiddleware;
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// Bad: Making everything pub
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pub fn internal_helper() {} // Should be pub(crate) or private
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```
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## 工具集成
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### 基本命令
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```bash
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# Build and check
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cargo build
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cargo check # Fast type checking without codegen
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cargo clippy # Lints and suggestions
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cargo fmt # Format code
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# Testing
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cargo test
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cargo test -- --nocapture # Show println output
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cargo test --lib # Unit tests only
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cargo test --test integration # Integration tests only
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# Dependencies
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cargo audit # Security audit
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cargo tree # Dependency tree
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cargo update # Update dependencies
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# Performance
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cargo bench # Run benchmarks
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```
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## 快速参考：Rust 惯用法
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| 惯用法 | 描述 |
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|-------|-------------|
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| 借用，而非克隆 | 传递 `&T`，除非需要所有权，否则不要克隆 |
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| 使非法状态无法表示 | 使用枚举仅对有效状态进行建模 |
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| `?` 优于 `unwrap()` | 传播错误，切勿在库/生产代码中恐慌 |
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| 解析，而非验证 | 在边界处将非结构化数据转换为类型化结构体 |
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| Newtype 用于类型安全 | 将基本类型包装在 newtype 中以防止参数错位 |
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| 优先使用迭代器而非循环 | 声明式链更清晰且通常更快 |
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| 对 Result 使用 `#[must_use]` | 确保调用者处理返回值 |
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| 使用 `Cow` 实现灵活的所有权 | 当借用足够时避免分配 |
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| 穷尽匹配 | 业务关键枚举不使用通配符 `_` |
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| 最小化 `pub` 接口 | 内部 API 使用 `pub(crate)` |
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## 应避免的反模式
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```rust
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// Bad: .unwrap() in production code
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let value = map.get("key").unwrap();
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// Bad: .clone() to satisfy borrow checker without understanding why
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let data = expensive_data.clone();
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process(&original, &data);
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// Bad: Using String when &str suffices
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fn greet(name: String) { /* should be &str */ }
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// Bad: Box<dyn Error> in libraries (use thiserror instead)
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fn parse(input: &str) -> Result<Data, Box<dyn std::error::Error>> { todo!() }
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// Bad: Ignoring must_use warnings
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let _ = validate(input); // Silently discarding a Result
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// Bad: Blocking in async context
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async fn bad_async() {
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std::thread::sleep(Duration::from_secs(1)); // Blocks the executor!
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// Use: tokio::time::sleep(Duration::from_secs(1)).await;
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}
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```
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**请记住**：如果它能编译，那它很可能是正确的 —— 但前提是你要避免 `unwrap()`，最小化 `unsafe`，并让类型系统为你工作。
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