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

Swift version: 5.1

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.

Available from iOS 9.0