在Rust中要用Struct和Enum组织数据的原因解析

// 未使用struct的代码
fn print_user(name: String, age: u8, email: String) {
    println!("用户: {}, 年龄: {}, 邮箱: {}", name, age, email);
}
fn main() {
    let name = String::from("张三");
    let age = 25;
    let email = String::from("zhangsan@example.com");
    // 问题：参数顺序容易出错！
    print_user(email, age, name); // 错误：邮箱和用户名传反了
}

struct User {
    name: String,
    age: u8,
    email: String,
}
fn print_user(user: &User) {
    println!(
        "用户: {}, 年龄: {}, 邮箱: {}",
        user.name, user.age, user.email
    );
}
fn main() {
    let user = User {
        name: String::from("张三"),
        age: 25,
        email: String::from("zhangsan@example.com"),
    };
    print_user(&user); // 正确：字段通过结构体明确关联
}

// 未使用enum的代码
struct Message {
    kind: String,  // 用字符串标记类型："text", "image", "video"
    content: String,
}
fn process_message(msg: &Message) {
    if msg.kind == "text" {
        println!("收到文本: {}", msg.content);
    } else if msg.kind == "image" {
        println!("收到图片: {}", msg.content);
    } else {
        // 潜在问题：可能遗漏某些类型！
        panic!("未知消息类型");
    }
}

enum Message {
    Text(String),
    Image { url: String, width: u32, height: u32 },
    Video(String),
}
fn process_message(msg: &Message) {
    match msg {
        Message::Text(text) => println!("收到文本: {}", text),
        Message::Image { url, width, height } => {
            println!("收到图片: {} (尺寸: {}x{})", url, width, height)
        }
        Message::Video(url) => println!("收到视频: {}", url),
    }
}
fn main() {
    let msg1 = Message::Text(String::from("你好！"));
    let msg2 = Message::Image {
        url: String::from("https://example.com/image.jpg"),
        width: 800,
        height: 600,
    };
    process_message(&msg1);
    process_message(&msg2);
}

// 定义数据包类型
enum Packet {
    Login(LoginData),
    Logout(LogoutData),
}
// 登录包的数据结构
struct LoginData {
    username: String,
    password: String,
}
// 登出包的数据结构
struct LogoutData {
    timestamp: u64,
}
fn parse_packet(packet: Packet) {
    match packet {
        Packet::Login(data) => {
            println!(
                "登录请求 - 用户名: {}, 密码: {}",
                data.username, data.password
            )
        }
        Packet::Logout(data) => {
            println!("登出时间: {}", data.timestamp)
        }
    }
}
fn main() {
    let login_packet = Packet::Login(LoginData {
        username: String::from("user123"),
        password: String::from("secret"),
    });
    let logout_packet = Packet::Logout(LogoutData {
        timestamp: 1629782400,
    });
    parse_packet(login_packet);
    parse_packet(logout_packet);
}

enum Message {
    Text(String),
    Image { url: String, width: u32, height: u32 },
    Video(String),
    Audio(String), // 新增变体
}
fn process_message(msg: &Message) {
    match msg {
        Message::Text(text) => println!("收到文本: {}", text),
        Message::Image { url, width, height } => {
            println!("收到图片: {} (尺寸: {}x{})", url, width, height)
        }
        // 编译器会报错：未处理 `Message::Audio` 分支！
    }
}

// 定义一个“形状”枚举
enum Shape {
    Circle { radius: f64 },
    Rectangle { width: f64, height: f64 },
}
// 为枚举实现方法
impl Shape {
    fn area(&self) -> f64 {
        match self {
            Shape::Circle { radius } => std::f64::consts::PI * radius * radius,
            Shape::Rectangle { width, height } => width * height,
        }
    }
}
fn main() {
    let circle = Shape::Circle { radius: 3.0 };
    let rect = Shape::Rectangle {
        width: 4.0,
        height: 5.0,
    };
    println!("圆形面积: {:.2}", circle.area()); // 输出: 28.27
    println!("矩形面积: {:.2}", rect.area());   // 输出: 20.00
}