rustlings/exercises/traits/traits2.rs

// traits2.rs
//
// Your task is to implement the trait
// `AppendBar` for a vector of strings.
//
// To implement this trait, consider for
// a moment what it means to 'append "Bar"'
// to a vector of strings.
//
// No boiler plate code this time,
// you can do this!
// Execute `rustlings hint traits2` or use the `hint` watch subcommand for a hint.

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

// TODO: Implement trait `AppendBar` for a vector of strings.
impl AppendBar for Vec<String> {
    // In other words, when a value is owned, its mutability is not part of the type, only the binding. When calling a function or implementing a trait, only the types have to match, not the patterns of the parameters
    // When a value is moved, it doesn't matter for the method declaration whether or not it is mutated. An owned value can always be made mutable anyway: let mut x = x;
    fn append_bar(mut self) -> Self {
        self.push("Bar".into());
        self
    }
}

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

    #[test]
    fn is_vec_pop_eq_bar() {
        let mut foo = vec![String::from("Foo")].append_bar();
        assert_eq!(foo.pop().unwrap(), String::from("Bar"));
        assert_eq!(foo.pop().unwrap(), String::from("Foo"));
    }
}