Rust Programming By Example

Playing with moves

Instead of taking &mut every time, we'll directly take the object's ownership every time:

struct Number(u32);

impl Number {
    fn new(nb: u32) -> Number {
        Number(nb)
    }

    fn add(mut self, other: u32) -> Number {
        self.0 += other;
        self
    }

    fn sub(mut self, other: u32) -> Number {
        self.0 -= other;
        self
    }
}

Then, there's no more need for the ending method:

let nb = Number::new(0).add(10).sub(5).add(12);
assert_eq!(nb.0, 17);

I generally prefer this way of doing builder patterns but it's more of a personal opinion than a thoughtful decision. Pick whichever seems to fit the best in your situation!