trait

code:trait.rs

pub trait Summary {

fn summarize(&self) -> String;

}

pub struct NewsArticle {

pub headline: String,

pub location: String,

pub author: String,

pub content: String,

}

impl Summary for NewsArticle {

fn summarize(&self) -> String {

format!("{}, by {} ({})", self.headline, self.author, self.location)

}

}

pub fn notify(item: &impl Summary) {

println!("Breaking news! {}", item.summarize());

}

// 以下のように書いてもよい

pub fn notify<T: Summary>(item: &T) {

println!("Breaking news! {}", item.summarize());

}

// 以下のように書いてもよい

pub fn notify<T>(item: &T) where T: Summary {

}

デフォルト実装を提供できる

code:.rs

pub trait Summary {

fn summarize(&self) -> String {

// "（もっと読む）"

String::from("(Read more...)")

}

}

code:.rs

pub fn notify(item: &(impl Summary + Display)) {