Rust 泛型、特征与生命周期详解

泛型编程

泛型函数

// 泛型函数：找出最大值
fn largest<T: PartialOrd>(list: &[T]) -> &T {let mut largest = &list[0];for item in list {if item > largest {largest = item;}}largest
}fn main() {let numbers = vec![34, 50, 25, 100, 65];let chars = vec!['y', 'm', 'a', 'q'];println!("最大数字：{}", largest(&numbers));println!("最大字符：{}", largest(&chars));
}

泛型结构体

// 通用的点坐标结构体
struct Point<T> {x: T,y: T,
}// 混合类型的点
struct MixedPoint<T, U> {x: T,y: U,
}fn main() {// 整数点let integer_point = Point { x: 5, y: 10 };// 浮点数点let float_point = Point { x: 1.0, y: 4.0 };// 混合类型点let mixed_point = MixedPoint { x: 5, y: 4.0 };
}

泛型枚举

// Option 枚举的泛型实现
enum Option<T> {Some(T),None,
}// Result 枚举的泛型实现
enum Result<T, E> {Ok(T),Err(E),
}fn main() {let some_number: Option<i32> = Option::Some(5);let some_string: Option<String> = Option::Some(String::from("hello"));
}

泛型方法

impl<T> Point<T> {fn x(&self) -> &T {&self.x}
}// 特定类型的方法
impl Point<f64> {fn distance_from_origin(&self) -> f64 {(self.x.powi(2) + self.y.powi(2)).sqrt()}
}

特征（Trait）

特征定义

// 定义特征
trait Summary {fn summarize(&self) -> String;// 带默认实现的方法fn default_summary(&self) -> String {String::from("...")}
}struct NewsArticle {headline: String,author: String,
}// 为类型实现特征
impl Summary for NewsArticle {fn summarize(&self) -> String {format!("{}, by {}", self.headline, self.author)}
}

特征约束

// 特征作为参数约束
fn notify<T: Summary>(item: &T) {println!("Breaking news! {}", item.summarize());
}// 多特征约束
fn process<T: Summary + Display>(item: &T) {println!("{}", item.summarize());
}// where 子句简化复杂约束
fn complex_function<T, U>(t: &T, u: &U) 
where T: Summary + Clone,U: Display + Debug 
{// 函数体
}

特征对象

trait Draw {fn draw(&self);
}struct Button {width: u32,
}struct TextField {placeholder: String,
}impl Draw for Button {fn draw(&self) {println!("绘制按钮");}
}impl Draw for TextField {fn draw(&self) {println!("绘制文本框");}
}// 使用特征对象
fn render(components: &[&dyn Draw]) {for component in components {component.draw();}
}

派生特征

// 自动实现常用特征
#[derive(Debug, Clone, PartialEq)]
struct Person {name: String,age: u32,
}

生命周期

生命周期注解

// 生命周期标注
fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {if x.len() > y.len() { x } else { y }
}// 结构体中的生命周期
struct ImportantExcerpt<'a> {part: &'a str,
}

生命周期省略规则

// 编译器自动推断生命周期
fn first_word(s: &str) -> &str {let bytes = s.as_bytes();for (i, &item) in bytes.iter().enumerate() {if item == b' ' {return &s[0..i];}}&s[..]
}

生命周期约束

// 复杂生命周期约束
fn longest_with_announcement<'a, T>(x: &'a str, y: &'a str, ann: T
) -> &'a str 
where T: Display 
{println!("公告：{}", ann);if x.len() > y.len() { x } else { y }
}