An impl Block Gives a Rust Struct Methods

A method is defined in an impl block and is called on an instance with dot syntax. Its first parameter is a form of self, which represents the instance receiving the call in source.

This must feel very similar to other languages that support struct or classes and methods

struct Rectangle {
    width: u32,
    height: u32,
}
 
impl Rectangle {
    fn area(&self) -> u32 {
        self.width * self.height
    }
}
 
fn main() {
    let rectangle = Rectangle {
        width: 30,
        height: 50,
    };
 
    println!("Area: {}", rectangle.area());
    println!("Width: {}", rectangle.width);
}

impl Rectangle groups this behavior with the Rectangle type. The area method reads the fields of the particular instance on which we call it. We write rectangle.area() rather than passing rectangle as an explicit argument. &self means the method borrows that instance, so the next line can still use rectangle