Functional Programming: A PragPub Anthology

Instance Methods Are Curried Functions

One cool thing to note is that instance methods are actually curried functions in Swift.

The basic idea behind currying is that a function can be partially applied, meaning that some of its parameter values can be specified (bound) before the function is called. Partial function application yields a new function.

So given that I have a class:

class MyHelloWorldClass {

    func helloWithName(name: String) -> String {
        return "hello, \(name)"
    }
}

I can create a variable that points to the class’s helloWithName function:

let helloWithNameFunc = MyHelloWorldClass.helloWithName
// MyHelloWorldClass -> (String) -> String

My new helloWithNameFunc is of type MyHelloWorldClass -> (String) -> String ...