How does one make an optional closure in swift?

Question

I\'m trying to declare an argument in Swift that takes an optional closure. The function I have declared looks like this:

class Promise {

 func then(onFulfi         


        

Answer 1

Maybe it's a cleaner way. Specially when the closure has complicated parameters.

typealias SimpleCallBack = () -> ()

class Promise {

func then(onFulfilled: SimpleCallBack, onReject: SimpleCallBack?){       
    if let callableRjector = onReject {
        // do stuff! 
    }
}

}