结构体

定义并实例化结构体

结构体定义

struct User {
    username: String,
    email: String,
    sign_in_count: u64,
    active: bool,
}

创建结构体

let user1 = User {
    email: String::from("someone@example.com"),
    username: String::from("someusername123"),
    active: true,
    sign_in_count: 1,
};

修改结构体示例中的字段

let user1 = User {
    email: String::from("someone@example.com"),
    username: String::from("someusername123"),
    active: true,
    sign_in_count: 1,
};
// 修改email值
user1.email = String::from("anotheremail@example.com");

接收邮箱和⽤户名作为参数并返回 User 实例的函数 build_user

fn build_user(email: String, username: String) -> User {
    User {
        username,
        email,
        active: true,
        sign_in_count: 1,
    }
}

根据其他实例创建新实例

let user2 = User {
    email: String::from("another@example.com"),
    username: String::from("anotherusername567"),
    active: user1.active,
    sign_in_count: user1.sign_in_count,
};

let user2 = User {
    email: String::from("another@example.com"),
    username: String::from("anotherusername567"),
    ..user1
};

元组的⽅式定义结构体

struct Color(i32, i32, i32);
struct Point(i32, i32, i32);

let black = Color(0, 0, 0);
let origin = Point(0, 0, 0);

⼀个使⽤结构体的⽰例程序

fn main() {
    let width1 = 30;
    let height1 = 30;

    println!(
        "The area of the rectangle is {} square pixels.",
        area(width1, height1)
    )
}

fn area(width: u32, height: u32) -> u32 {
    width * height
}

使⽤元组来重构代码

fn main() {
    let react1 = (30, 50);

    println!(
        "The area of the rectangle is {} square pixels.",
        area(react1)
    )
}

fn area(dimensions: (u32, u32)) -> u32 {
    dimensions.0 * dimensions.1
}

使用结构体来重构代码

struct Rectangle {
    width: u32,
    height: u32,
}

fn main() {
    let rect1 = Rectangle {
        width: 30,
        height: 50,
    };

    println!(
        "The area of the rectangle is {} square pixels.",
        area(&rect1)
    )
}

fn area(rectangle: &Rectangle) -> u32 {
    rectangle.width * rectangle.height
}

定义方法

#[derive(Debug)]
struct Rectangle {
    width: u32,
    height: u32,
}

impl Rectangle {
    fn area(&self) -> u32 {
        self.width * self.height
    }
}

fn main() {
    let rect1 = Rectangle {
        width: 30,
        height: 50,
    };

    println!(
        "The area of the rectangle is {} square pixels.",
        rect1.area()
    )
}

更多参数的⽅法

#[derive(Debug)]
struct Rectangle {
    width: u32,
    height: u32,
}

impl Rectangle {
    fn area(&self) -> u32 {
        self.width * self.height
    }
    fn can_hold(&self, other: &Rectangle) -> bool {
        self.width > other.width && self.height > other.height
    }
}

fn main() {
    let rect1 = Rectangle {
        width: 30,
        height: 50,
    };
    let rect2 = Rectangle {
        width: 10,
        height: 40,
    };
    let rect3 = Rectangle {
        width: 60,
        height: 45,
    };

    println!("Can rect1 hold rect2?{}", rect1.can_hold(&rect2));
    println!("Can rect1 hold rect3?{}", rect1.can_hold(&rect3));
}