Argument of '#selector' does not refer to an '@objc' method, property, or initializer

Question

I sublcassed in Swift 3 a UIButton subclass that is written in Objective-C.

When I try to add a target, it fails with an error code:

class ActionButton: JTImageButton {

    func action() {

    }

    func configure()) {
        // ...
        self.addTarget(self, action: #selector(self.action()), for: .touchUpInside)
        // error: 
        // Argument of '#selector' does not refer to an '@objc' method, property, or initializer

    }
}

Solution 1

All you have to do is mark the func as @objc and there's no need for the self reference or the parenthesis

class ActionButton: JTImageButton {

    @objc func btnAction() {

    }

    func configure() {
        // ...
        self.addTarget(self, action: #selector(btnAction), for: .touchUpInside)
        // error: 
        // Argument of '#selector' does not refer to an '@objc' method, property, or initializer

    }
}

You can even make it private if you want

Solution 2

The problem is that in #selector(self.action()), self.action() is a method call. You don't want to call the method; you want to name the method. Say #selector(action) instead: lose the parentheses, plus there's no need for the self.

Solution 3

Adding @objc keyword in the front the method that is perfect, but I still got this error. Finally, I found out the solution as follows

There is a pair of superfluous parentheses behind the method as picture shown above. What I should do is that remove it and it worked well.

Solution 4

Instead of saying self.action(), use ActionButton.action().

View more solutions

Comments

[MJQZ1347]

Thanks, but it says Ambiguous use of 'action' when I implemented your approach? Edit: Renaming action() to action2() helped.

[Martin R]

In addition, it conflicts with the action(for:, forKey:) method of UIView. #selector(action) will give an "ambiguous use" and your Q&A stackoverflow.com/questions/35658334/… applies.

[cjrieck]

Weird. I renamed the method to be btnAction and it doesn't give me that error. Maybe something to do with the function name, action? I've updated my answer to show what I mean

[Ashok R]

so func action() { } has to be repalced with some other name as @matt said otherwise you will end up with Ambiguous use of action() error.

[Martin R]

You don't need the @objc because the class already inherits from NSObject.

[cjrieck]

True. Since it's a public method on an NSObject there's no need for the @objc. If the func were to be made private it would be needed

[Admin]

Agreed. I'll point that out in my answer. I was answering the intent of the question, not the technicals. I shouldn't do that!

[Papershine]

This doesn't answer the question's needs. Also, please don't repost answers.

[Johnny]

This is the answer I came across, and someone may encounter too. And I solved it by removing the parenthesis. Why you downvoted my answer? It's REAL answer! @paper1111

[Krunal Nagvadia]

What if function with more than one Argument?

[matt]

What if it does?

[Let.Simoo]

What if the named func has more than one Argument... how and where to fill those Arguments??

[matt]

@Let.Simoo There are no arguments in a #selector expression. You are describing the method, not calling it.