結構體（structs）

• 沒有成員的單元結構體
• 有成員但沒有名字的元組結構體
• 有成員而且有名字的普通結構體

// 結構體
struct Point {
    x: i32,
    y: i32,
}
// 不變繫結
let origin = Point { x: 0, y: 0 }; // origin: Point
println!("The origin is at ({}, {})", origin.x, origin.y);
// 可變繫結
let mut point = Point { x: 0, y: 0 };
point.x = 5;
// 更新語法（update syntax）
struct Point3d {
    x: i32,
    y: i32,
    z: i32,
}
let mut point = Point3d { x: 0, y: 0, z: 0 };
point = Point3d { y: 1, .. point };
// 元組結構體（tuple structs）
struct Color(i32, i32, i32);
struct Point(i32, i32, i32);
let black = Color(0, 0, 0);
let origin = Point(0, 0, 0);
// 單元結構體（unit-like structs）
struct Electron;
let x = Electron;
 

方法語法（method-syntax）

// 方法語法
struct Circle {
    x: f64,
    y: f64,
    radius: f64,
}
impl Circle {
    // 要實現方法呼叫（method calls）語法，第一個引數必須是self的某種形式
    fn area(&self) -> f64 {
        std::f64::consts::PI * (self.radius * self.radius)
    }
    // 通過返回結構體來實現鏈式方法呼叫（chaining method calls）
    fn grow(&self, increment: f64) -> Circle {
        Circle { x: self.x, y: self.y, radius: self.radius + increment }
    }
    // 通過返回結構體來實現關聯函式（associated functions）
    fn new(x: f64, y: f64, radius: f64) -> Circle {
        Circle {
            x: x,
            y: y,
            radius: radius,
        }
    }
}
impl Circle {
    // self引數只有不變借用，可變借用和移動這三種形式
    fn reference(&self) {
       println!("taking self by reference!");
    }
    fn mutable_reference(&mut self) {
       println!("taking self by mutable reference!");
    }
    fn takes_ownership(self) {
       println!("taking ownership of self!");
    }
}
fn main() {
    let c = Circle { x: 0.0, y: 0.0, radius: 2.0 };
    // 方法呼叫
    println!("{}", c.area());
    // 關聯函式
    let c = Circle::new(0.0, 0.0, 2.0);
    // 鏈式方法呼叫
    let d = c.grow(2.0).area();
    println!("{}", d);
}
 

列舉（enums）

// 列舉
enum Message {
    Quit,
    ChangeColor(i32, i32, i32),
    Move { x: i32, y: i32 },
    Write(String),
}
let x: Message = Message::Move { x: 3, y: 4 };
let m = Message::Write("Hello, world".to_string());
let v = Message::ChangeColor(r, g, b);

模式（patterns）匹配（match）

// 匹配常量
let x = 1;
match x {
    1 => println!("one"),
    2 => println!("two"),
    3 => println!("three"),
    _ => println!("anything"),
}
// 匹配多個模式
let x = 1;
match x {
    1 | 2 => println!("one or two"),
    3 => println!("three"),
    _ => println!("anything"),
}
// 匹配結構
struct Point {
    x: i32,
    y: i32,
}
let origin = Point { x: 0, y: 0 };
match origin {
    Point { x, y } => println!("({},{})", x, y),
}
match origin {
    Point { x: x1, y: y1 } => println!("({},{})", x1, y1),
}
match origin {
    Point { x, .. } => println!("x is {}", x),
}
match origin {
    Point { y, .. } => println!("y is {}", y),
}
// 匹配列舉
enum Message {
    Quit,
    ChangeColor(i32, i32, i32),
    Move { x: i32, y: i32 },
    Write(String),
}
fn quit() { /* ... */ }
fn change_color(r: i32, g: i32, b: i32) { /* ... */ }
fn move_cursor(x: i32, y: i32) { /* ... */ }
fn process_message(msg: Message) {
    match msg {
        Message::Quit => quit(),
        Message::ChangeColor(r, g, b) => change_color(r, g, b),
        Message::Move { x: x, y: y } => move_cursor(x, y),
        Message::Write(s) => println!("{}", s),
    };
}
// 匹配中忽略某些值
// 匹配Result<R,E>時忽略某些值
match some_value {
    Ok(value) => println!("got a value: {}", value),
    Err(_) => println!("an error occurred"),
}
// 匹配元組時忽略某些值
fn coordinate() -> (i32, i32, i32) {
    // generate and return some sort of triple tuple
}
let (x, _, z) = coordinate();
let tuple: (u32, String) = (5, String::from("five"));
let (x, s) = tuple; // 匹配時String被移動
let (x, _) = tuple; // 匹配時String被忽略
// 匹配列舉時忽略某些值
enum OptionalTuple {
    Value(i32, i32, i32),
    Missing,
}
let x = OptionalTuple::Value(5, -2, 3);
match x {
    OptionalTuple::Value(..) => println!("Got a tuple!"),
    OptionalTuple::Missing => println!("No such luck."),
}
// 匹配後得到不變引用
let x = 5;
match x {
    ref r => println!("Got a reference to {}", r),
}
// 匹配後得到可變引用
let mut x = 5;
match x {
    ref mut mr => println!("Got a mutable reference to {}", mr),
}
// 匹配區間
let x = 1;
match x {
    1 ... 5 => println!("one through five"),
    _ => println!("anything"),
}
let x = ',';
match x {
    'a' ... 'j' => println!("early letter"),
    'k' ... 'z' => println!("late letter"),
    _ => println!("something else"),
}
// 匹配時繫結區間到變數名
let x = 1;
match x {
    e @ 1 ... 5 | e @ 8 ... 10 => println!("got a range element {}", e),
    _ => println!("anything"),
}
// 匹配複雜結構體時繫結某一部分到變數名
#[derive(Debug)]
struct Person {
    name: Option,
}
let name = "Steve".to_string();
let mut x: Option = Some(Person { name: Some(name) });
match x {
    Some(Person { name: ref a @ Some(_), .. }) => println!("{:?}", a),
    _ => {}
}
// 匹配守衛（guards）即匹配時新增條件限制
enum OptionalInt {
    Value(i32),
    Missing,
}
let x = OptionalInt::Value(5);
match x {
    OptionalInt::Value(i) if i > 5 => println!("Got an int bigger than five!"),
    OptionalInt::Value(..) => println!("Got an int!"),
    OptionalInt::Missing => println!("No such luck."),
}
// 守衛的優先順序比多重模式要低
let x = 4;
let y = false;
match x {
    4 | 5 if y => println!("yes"),
    _ => println!("no"),
}