Overriding method with selector 'touchesBegan:withEvent:' has incompatible type '(NSSet, UIEvent) -> ()'

Question

Xcode 6.3. Within a class implementing UITextFieldDelegate protocol, I would like to override touchesBegan() method to possibly hide the keyboard. If I avoid a compiler error in the function spec, then there is a complier error trying to read the "touch" from the Set or NSSet, or else the super.touchesBegan(touches , withEvent:event) throws an error. One of these combinations compiled in Xcode 6.2! (So where is documentation to Swift "Set" and how to get an element from one?)

 override func touchesBegan(touches: NSSet, withEvent event: UIEvent) { 
    // Hiding the Keyboard when the User Taps the Background
        if let touch =  touches.anyObject() as? UITouch {
            if nameTF.isFirstResponder() && touch.view != nameTF {
                nameTF.resignFirstResponder();
            }
        }
        super.touchesBegan(touches , withEvent:event)
    }

Try:

override func touchesBegan(touches: NSSet, withEvent event: UIEvent) or
override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent) 

Compiler error: Overriding method with selector 'touchesBegan:withEvent:' has incompatible type '(NSSet, UIEvent) -> ()' and

super.touchesBegan(touches , withEvent:event)

also complains

'NSSet' is not implicitly convertible to 'Set'; did you mean to use 'as' to explicitly convert?

Try:

override func touchesBegan(touches: Set<AnyObject>, withEvent event: UIEvent) 

Compiler error: Type 'AnyObject' does not conform to protocol 'Hashable'

Try:

override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) 

Compiler error at

if let touch = touches.anyObject() as? UITouch 

'Set' does not have a member named 'anyObject' BUT the function spec and call to super() are OK!

Try:

override func touchesBegan(touches: NSSet<AnyObject>, withEvent event: UIEvent) -> () or
override func touchesBegan(touches: NSSet<NSObject>, withEvent event: UIEvent) 

Compiler error: Cannot specialize non-generic type 'NSSet'

Skink

Answer 1

Swift 1.2 (Xcode 6.3) introduced a native Set type that bridges with NSSet. This is mentioned in the Swift blog and in the Xcode 6.3 release notes, but apparently not yet added to the official documentation (update: As Ahmad Ghadiri noted, it is documented now).

The UIResponder method is now declared as

func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent)

and you can override it like this:

override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
    if let touch = touches.first as? UITouch {
        // ...
    }
    super.touchesBegan(touches , withEvent:event)
}

Update for Swift 2 (Xcode 7): (Compare Override func error in Swift 2)

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
    if let touch = touches.first {
        // ...
    }
    super.touchesBegan(touches, withEvent:event)
}

Update for Swift 3:

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    if let touch = touches.first {
        // ...
    }
    super.touchesBegan(touches, with: event)
}

Panocha

Thanks Martin R, All I had to do was change my NSSet to Set<NSObject> and my code is functioning. – Risorgimento

Hi @Martin Why super.touchesBegan(touches , withEvent:event) is need? I am still not understand Swift very well. – Inscription

I feel like it needs to be this: super.touchesBegan(touches, withEvent:event!) for xCode 7.2 – Gantrisin

@EugeneGordin: Why do you think so? The last method still compiles with Xcode 7.2. – Panocha

it was complaining for me...value of optional type not unwrapped – Gantrisin

@ZigiiWong because it's the superclass that eventually communicates/transfer the touch, event and makes the UI change. Things won't be managed properly.... – Apparitor

Answer 2

With xCode 7 and swift 2.0, use following code:

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {

    if let touch =  touches.first{
        print("\(touch)")
    }
    super.touchesBegan(touches, withEvent: event)
}

override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {

    if let touch = touches.first{
        print("\(touch)")
    }
    super.touchesEnded(touches, withEvent: event)
}

override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {

    if let touch = touches.first{
        print("\(touch)")
    }
    super.touchesMoved(touches, withEvent: event)
}

Cauley

I can't build the project. Getting error Method does not override any method from its superclass for the touchesBegan function. I tried to subclass from UIGestureRecognizer and UTapGestureRecognizer. Xcode 7.1 – Damson

use this #30892754 to check what going on with your code – Cauley

Answer 3

Using Swift 3 and Xcode 8

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

}

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {

}

override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {

}

override func touchesCancelled(_ touches: Set<UITouch>?, with event: UIEvent?) {
// Don't forget to add "?" after Set<UITouch>
}

Mahoney

Answer 4

It is now in the Apple API reference here and for overriding in xCode version 6.3 and swift 1.2 you can use this code:

override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
    if let touch =  touches.first as? UITouch {
         // ...
    }
    // ...
}

Adularia

Interesting that the online docs are correct but the version included in the Xcode help system is out-of-date. I guess I need to get in the habit of searching for this stuff online. – Shadrach

Answer 5

The current one right now for the newest update as of xCode 7.2 Swift 2.1 on Dec 19, 2015.

Next time you get an error like this again, remove the function and start typing it again "touchesBe..." and xCode should automatically complete it to the newest one for you instead of trying to fix the old one.

override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {

    for touch: AnyObject! in touches {
        let touchLocation = touch.locationInNode(self)

        //Use touchLocation for example: button.containsPoint(touchLocation) meaning the user has pressed the button.
    }
}

Jamaaljamaica

Answer 6

What worked for me was:

    override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
        if let touch = touches.first as? UITouch {
            // ...
        }

        super.touchesBegan(touches , withEvent:event!)
    }

Clotildecloture

If you are on Xcode 6.3 and Swift 1.2 your code will not work. This post if referencing Xcode 6.3 and Swift 1.2. – Risorgimento

You are right, I updated Xcode today and it immediately gave error. – Clotildecloture

Answer 7

Small addition. For swift to compile w/o error, you need to add

import UIKit.UIGestureRecognizerSubclass

Solicitude

Answer 8

Using Swift 4 and Xcode 9

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

}

Fearless

Answer 9

  override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

        if let touch = touches.first as? UITouch {

            if touch.view == self.view{
                self.dismiss(animated: true, completion: nil)
            }
        }
    }

Buber

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