Rust Programming By Example

Methods

We can add methods on custom types. Let's write a method to compute the distance of a point to the origin:

impl Point {
    fn dist_from_origin(&self) -> f64 {
        let sum_of_squares = self.x.pow(2) + self.y.pow(2);
        (sum_of_squares as f64).sqrt()
    }
}

There are a lot of new syntaxes here (impl Point, as, and .method()), so let's explain all of them. First of all, methods of a type are declared within the impl Type {} construct. This method takes a special parameter: &self. This parameter is the instance the method is called on, like this in other programming languages. The & operator before self means that the instance is passed by immutable reference. As we can see, it is possible to call methods on basic types in Rust—self.x.pow(2) computes ...