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1.1 结构体 ​

1. 结构体的写法 ​

普通的结构体 ​

rust
struct User {
  name: String,
  age: u16,
}
struct User {
  name: String,
  age: u16,
}

单元结构体 ​

rust
struct User;
struct User;

元组结构体 ​

rust
// 一个值的元组
struct User(String);

// 两个值的元组
struct User(String, u32);
// 一个值的元组
struct User(String);

// 两个值的元组
struct User(String, u32);

匿名结构体 ​

rust
{x:1,y:1}
{x:1,y:1}

2.结构体的初始化 ​

rust
let user = User {
    email: "someone@example.com",
    username: "someusername123",
    active: true,
    sign_in_count: 1,
};
let user = User {
    email: "someone@example.com",
    username: "someusername123",
    active: true,
    sign_in_count: 1,
};

3. 结构体更新值 ​

第一种, 直接修改单个值

rust
let mut user = User {
    active: true,
    username: String::from("value"),
    email: String::from("value"),
    sign_in_count: 12,
};
user.active = false
let mut user = User {
    active: true,
    username: String::from("value"),
    email: String::from("value"),
    sign_in_count: 12,
};
user.active = false

第二种，修改多个

rust
let user2 = User {
    email: String::from("email"),
    username: String::from("username"),
    ..user
};
let user2 = User {
    email: String::from("email"),
    username: String::from("username"),
    ..user
};

2. 如何打印结构体 ​

rust
#[derive(Debug)] // 关键是这行
struct Rectangle {
    width: u32,
    height: u32,
}

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

    println!("rect1 is {:?}", rect1);
}
#[derive(Debug)] // 关键是这行
struct Rectangle {
    width: u32,
    height: u32,
}

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

    println!("rect1 is {:?}", rect1);
}

3.结构体的属性怎么用引用类型 ​

正常来讲结构体拥有它所有的数据，而不是从其它地方借用数据。

你也可以让 User 结构体从其它对象借用数据，不过这么做，就需要引入生命周期(lifetimes)这个新概念

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

fn main() {
    let user1 = User {
        email: "someone@example.com",
        username: "someusername123",
        active: true,
        sign_in_count: 1,
    };
}
struct User {
    username: &str,
    email: &String,
    sign_in_count: u64,
    active: bool,
}

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

比如上面的&str和&String是一个引用，这里会报错