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教程 rust tutorial

枚举 Enums

枚举用于定义一组有限的可能值，常用于状态机、错误处理等场景。

定义枚举

rust 
enum Message {
    Quit,
    Move { x: i32, y: i32 },
    Write(String),
    ChangeColor(i32, i32, i32),
}

使用枚举

rust 
fn main() {
    let msg = Message::Write(String::from("hello"));
    match msg {
        Message::Quit => println!("Quit"),
        Message::Move { x, y } => println!("Move to ({}, {})", x, y),
        Message::Write(text) => println!("Text message: {}", text),
        Message::ChangeColor(r, g, b) => println!("Change color to RGB({}, {}, {})", r, g, b),
    }
}

关联数据

枚举成员可以携带数据，支持多样化表达。

Option 枚举

Rust 标准库中的 Option<T> 是枚举的经典示例，用于表示有或无值：

rust 
let some_number = Some(5);
let absent_number: Option<i32> = None;
Rust Playground
打开运行 
enum Message {
    Quit,
    Move { x: i32, y: i32 },
    Write(String),
    ChangeColor(i32, i32, i32),
}

fn main() {
let msg = Message::Write(String::from("hello"));
match msg {
Message::Quit => println!("Quit"),
Message::Move { x, y } => println!("Move to ({}, {})", x, y),
Message::Write(text) => println!("Text message: {}", text),
Message::ChangeColor(r, g, b) => println!("Change color to RGB({}, {}, {})", r, g, b),
}
}

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