การกำหนดคุณลักษณะ

trait Greet {
    fn hello(&self) -> String;
}

fn main() {
    println!("trait declared");
}

trait Greet {
    fn hello(&self) -> String;
}

struct Dog;

impl Greet for Dog {
    fn hello(&self) -> String {
        String::from("Woof")
    }
}

fn main() {
    let d = Dog;
    println!("{}", d.hello());
}

trait Greet { fn hello(&self) -> String; }

struct Dog;
struct Cat;

impl Greet for Dog { fn hello(&self) -> String { String::from("Woof") } }
impl Greet for Cat { fn hello(&self) -> String { String::from("Meow") } }

fn main() {
    println!("{}", Dog.hello());
    println!("{}", Cat.hello());
}

trait Greet { fn hello(&self) -> String; }
struct Dog;
impl Greet for Dog { fn hello(&self) -> String { String::from("Woof") } }

fn announce(g: &impl Greet) {
    println!("It says: {}", g.hello());
}

fn main() {
    announce(&Dog);
}

trait Greet { fn hello(&self) -> String; }
struct Cat;
impl Greet for Cat { fn hello(&self) -> String { String::from("Meow") } }

fn shout<T: Greet>(g: &T) {
    println!("{}!", g.hello().to_uppercase());
}

fn main() {
    shout(&Cat);
}

trait Named { fn name(&self) -> String; }

#[derive(Clone)]
struct Item { label: String }

impl Named for Item {
    fn name(&self) -> String { self.label.clone() }
}

fn describe<T: Named + Clone>(t: &T) {
    let copy = t.clone();
    println!("named {}", copy.name());
}

fn main() {
    describe(&Item { label: String::from("box") });
}

use std::fmt::Debug;

fn print_all<T>(items: &[T])
where
    T: Debug,
{
    for it in items {
        println!("{:?}", it);
    }
}

fn main() {
    print_all(&[1, 2, 3]);
}

trait Shape {
    fn area(&self) -> f64;
    fn name(&self) -> String;
}

struct Square { side: f64 }

impl Shape for Square {
    fn area(&self) -> f64 { self.side * self.side }
    fn name(&self) -> String { String::from("square") }
}

fn main() {
    let s = Square { side: 3.0 };
    println!("{} area {}", s.name(), s.area());
}