Traits

Traits กำหนด behavior ที่ types ต้องมี คล้าย interfaces ในภาษาอื่น

นิยาม Trait

trait Summary {
    fn summarize(&self) -> String;
}

Implement Trait

trait Summary {
    fn summarize(&self) -> String;
}

struct Article {
    title: String,
    author: String,
    content: String,
}

impl Summary for Article {
    fn summarize(&self) -> String {
        format!("{} by {}", self.title, self.author)
    }
}

struct Tweet {
    username: String,
    content: String,
}

impl Summary for Tweet {
    fn summarize(&self) -> String {
        format!("@{}: {}", self.username, self.content)
    }
}

fn main() {
    let article = Article {
        title: String::from("Rust is great"),
        author: String::from("Alice"),
        content: String::from("..."),
    };

    println!("{}", article.summarize());
}

Default Implementation

trait Summary {
    fn summarize(&self) -> String {
        String::from("(Read more...)")
    }
}

struct Article {
    title: String,
}

impl Summary for Article {} // ใช้ default

fn main() {
    let article = Article { title: String::from("News") };
    println!("{}", article.summarize()); // (Read more...)
}

Traits as Parameters

fn notify(item: &impl Summary) {
    println!("Breaking news! {}", item.summarize());
}

// หรือใช้ trait bound syntax
fn notify2<T: Summary>(item: &T) {
    println!("Breaking news! {}", item.summarize());
}

Derive Attribute

#[derive(Debug, Clone, PartialEq)]
struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let p1 = Point { x: 1, y: 2 };
    let p2 = p1.clone();

    println!("{:?}", p1);
    println!("Equal: {}", p1 == p2);
}

Common derives: Debug, Clone, Copy, PartialEq, Eq, Hash, Default

สรุป

👉 ต่อไป: Trait Bounds