rustlings/exercises/traits/traits1.rs

// traits1.rs
// Time to implement some traits!
//
// Your task is to implement the trait
// `AppendBar` for the type `String`.
//
// The trait AppendBar has only one function,
// which appends "Bar" to any object
// implementing this trait.
// Execute `rustlings hint traits1` or use the `hint` watch subcommand for a hint.

trait AppendBar {
    fn append_bar(self) -> Self;
}

impl AppendBar for String {
    fn append_bar(self) -> String {
        format!("{}Bar", self)
    } 
}

fn main() {
    let s = String::from("Foo");
    let s = s.append_bar();
    println!("s: {}", s);
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn is_foo_bar() {
        assert_eq!(String::from("Foo").append_bar(), String::from("FooBar"));
    }

    #[test]
    fn is_bar_bar() {
        assert_eq!(
            String::from("").append_bar().append_bar(),
            String::from("BarBar")
        );
    }
}