What’s the difference between a function and a method?

Swift version: 5.2

Paul Hudson @twostraws May 28th 2019

Some folks use “function” and “method” interchangeably, but there’s a small difference: both of them are reusable chunks of code, but methods belong to classes, structs, and enums, whereas functions do not.

So:

func thisIsAFunction() {
}

struct Person {
    func thisIsAMethod() {
    }
}

Because methods always belong to a data type, they have a concept of self that functions do not. This is a special value passed in by Swift, and it refers to whatever instance the method was called on.

Swift uses the same keyword, func, for both functions and methods.