Argument of '#selector' cannot refer to global function (Swift)

Question

I am trying to programatically add a UIBarButtonItem to my nav bar (which works), however I cannot get the action to work. What am I doing wrong?

I have the following code under viewDidLoad:

self.navigationItem.rightBarButtonItem = UIBarButtonItem(image: UIImage(named: "visualise"), style: .plain, target: self, action: #selector(visualise(sender:)))

And the following function declared outside the VC class:

func visualise(sender: UIBarButtonItem) {
// stuff to do once the button is tapped
}

I read a few answers saying the function cannot be local but that did not seem to help.

The selector must be part of the class referenced by the target. — rmaddy
– rmaddy, Commented Jun 23, 2018 at 22:41
You also need @objc before the function, otherwise you get a compiler error that the function is not exposed to Objective-C — paulo62
– paulo62, Commented Mar 19, 2020 at 16:53

Fogmeister · Accepted Answer · 2018-06-23 22:40:58Z

3

The function can not be “global”. That is what the error says.

If your function is declared outside the view controller then it is global.

You can only call instance (or static) functions from a selector.

The simplest change would be to put your function inside the view controller.

answered Jun 23, 2018 at 22:40

Fogmeister

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1 Comment

CristianMoisei Over a year ago

That worked like a charm, thanks a lot. What confused me was that I read someone saying it cannot be part of any class, so I thought I couldn't put it int he VC.

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