CODEWITHSUNDEEP
iosswiftselector
Nguyễn Anh Việt
Nguyễn Anh Việt

Reputation: 605

How to perform selector with a nested function?

I have a nested function like this and I want to call childFunc when user tap to my button, but it does not work

class MyClass {
    func parentFunc() {
        button.addTarget(self, action: #selector(parentFunc().childFunc), for: .touchUpInside)
        func childFunc() {
            print("User tapped")
        }
    }
}

It raise error like this: 

Value of tuple type '()' has no member 'childFunc'

Is there any way to perform childFunc with #selector ?

Edit 1: I have use closure like this, But I think it's not a nice way because I have to make another function

class MyClass {
    myClosure: () -> () = {}
    func parentFunc() {
        button.addTarget(self, action: #selector(runChildFunc), for: .touchUpInside)
        func childFunc() {
            print("User tapped")
        }
        myClosesure = childFunc

    }
    func runChildFunc() {
        myClosure()
    }
}

Upvotes: 2

Views: 735

Answers (2)

Govind Prajapati
Govind Prajapati

Reputation: 957

instead, you can try below code to achieve your goal 

class MyClass {
    let button = UIButton()

   @objc public func parentFunc(_ sender : UIButton?) 
      {

        func childFunc() {
         print("User tapped")
        }

        if sender != nil && sender.tag == 100{
        childFunc()
        return
        }

        button.addTarget(self, action: #selector(parentFunc(_:)), for: .touchUpInside)
        button.tag = 100
       }
    }

In above code, Sender is optional so you can pass nil when you don't want to call child function like parentFunc(nil)

Upvotes: 4

matt
matt

Reputation: 534925

Is there any way to perform childFunc with #selector

No. The entire idea makes no sense. Keep in mind that the nested (inner) func does not really exist. It only comes into existence, momentarily, when the outer func runs. The running of the outer func brings the inner func into existence at the moment the definition is encountered, effectively storing it in a local variable, so that it is callable from subsequent code in scope inside the func. And like any local variable, when the outer func code ends, the inner func goes back out of existence. Also, because it is a local variable inside the func, it is scoped in such a way that it couldn't be called into from outside, even if such a notion made sense — just as a local variable inside a func cannot be seen from outside the func, even if that notion made sense.

The selector must point to a method of a class instance (where the class derives from NSObject). This is a Cocoa Objective-C architecture; you have to obey Objective-C rules.

Upvotes: 3

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