Traits

• Define a set of behavior for other types to follow if they want to have this Trait

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 struct Tweet {
    pub username: String,
    pub content: String,
    pub reply: bool,
    pub retweet: bool,
}

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

use aggregator::{Summary, Tweet}; // Note that when we want to call the function that implements a trait, we also need to import the trait into the scope

fn main() {
    let tweet = Tweet {
        username: String::from("horse_ebooks"),
        content: String::from(
            "of course, as you probably already know, people",
        ),
        reply: false,
        retweet: false,
    };

    println!("1 new tweet: {}", tweet.summarize());
}

• We can also do default implementation when defining a trait

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

• Trait as parameters, basically means that any params need to implement the given

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