Swift 5 : How do you pass a function to run inside a function () Noobie in swift

Question

How can i pass a function to run inside a function when passing it inside a parameter? .. as example

func thisDelay(_ passFunc:() ){//
        let seconds = 5.0
        DispatchQueue.main.asyncAfter(deadline: .now() + seconds) {
            passFunc
            print("test2")
        }

thisDelay(print("Hello"))

//..Hello (is printed right away)
//.. test2 (is printed after 5 seconds)

// As seen Hello is printed right away .. shouldn't it been delayed with 5 sec?

Passing function as a completion block will help you. like -> **(_ passFunc: @escaping () -> Void )** and then calling it inside asynAfter like **passFunc()** — Saurabh Prajapati, Nov 23 '20 at 13:22
You are not passing a function, and `passFunc` is not typed as a function (it is a Void). Also, in `thisDelay` you are not _calling_ `passFunc`, you are just saying its name. — matt, Nov 23 '20 at 16:02

score 3 · Accepted Answer · answered Nov 23 '20 at 16:05

It's hard to list everything that's wrong with your code...

In the line thisDelay(print("Hello")), you are not passing any function. You're just printing, right then, as you call thisDelay.
In the declaration of thisDelay, the parameter passFunc is not typed as a function; it is a Void.
In the body of thisDelay, you are not calling passFunc (which you cannot do in any case, as it is not a function); you are just saying its name, which is useless.

You probably mean something like this:

func thisDelay(_ passFunc: @escaping () -> ()) {
    let seconds = 5.0
    DispatchQueue.main.asyncAfter(deadline: .now() + seconds) {
        passFunc()
        print("test2")
    }
}
thisDelay { print("Hello") }

But for a _real_ `delay` implementation see my https://stackoverflow.com/questions/24034544/dispatch-after-gcd-in-swift/24318861#24318861 — matt, Nov 23 '20 at 16:13

Swift 5 : How do you pass a function to run inside a function () Noobie in swift

1 Answers1