特征定义与实现 #

pub trait Summary {
    fn summarize(&self) -> String;
    
    // 默认实现
    fn default_summary(&self) -> String {
        String::from("默认摘要")
    }
}

pub struct NewsArticle {
    pub headline: String,
    pub content: String,
}

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

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

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

pub fn notify(item: &impl Summary) {
    println!("突发新闻! {}", item.summarize());
}

// 或使用 trait bound
pub fn notify2<T: Summary>(item: &T) {
    println!("突发新闻! {}", item.summarize());
}