Practice: lifetime qualifier added version of sample code at http://rustbyexample.com/trait.html

gistfile1.rs

struct Sheep<'a> { naked: bool, name: &'a str }

trait Animal<'a> {
    fn new(name: &'a str) -> Self;

    fn name(&self) -> &str;
    fn noise(&self) -> &str;

    fn talk(&self) {
        println!("{} says {}", self.name(), self.noise());
    }
}

impl <'a> Sheep<'a> {
    fn is_naked(&self) -> bool {
        self.naked
    }

    fn shear(&mut self) {
        if self.is_naked() {
            println!("{} is already naked...", self.name());
        } else {
            println!("{} gets a haircut!", self.name);
            self.naked = true;
        }
    }
}

impl <'a> Animal<'a> for Sheep<'a> {
    fn new(name: &str) -> Sheep {
        Sheep { name: name, naked: false }
    }

    fn name(&self) -> &str {
        self.name
    }

    fn noise(&self) -> &str {
        if self.is_naked() {
            "baaaaah?"
        } else {
            "baaaaah!"
        }
    }

    fn talk(&self) {
        println!("{} pauses briefly... {}", self.name, self.noise());
    }
}

fn main() {
    let mut dolly: Sheep = Animal::new("Dolly");

    dolly.talk();
    dolly.shear();
    dolly.talk();
}