How to set the action for a UIBarButtonItem in Swift

Question

How can the action for a custom UIBarButtonItem in Swift be set?

The following code successfully places the button in the navigation bar:

var b = UIBarButtonItem(title: "Continue", style: .Plain, target: self, action:nil)
self.navigationItem.rightBarButtonItem = b

Now, I would like to call func sayHello() { println("Hello") } when the button is touched. My efforts so far:

var b = UIBarButtonItem(title: "Continue", style: .Plain, target: self, action:sayHello:)
// also with `sayHello` `sayHello()`, and `sayHello():`

and..

var b = UIBarButtonItem(title: "Continue", style: .Plain, target: self, action:@selector(sayHello:))
// also with `sayHello` `sayHello()`, and `sayHello():`

and..

var b = UIBarButtonItem(title: "Continue", style: .Plain, target: self, action:@selector(self.sayHello:))
// also with `self.sayHello` `self.sayHello()`, and `self.sayHello():`

Note that sayHello() appears in the intellisense, but does not work.

Thanks for your help.

EDIT: For posterity, the following works:

var b = UIBarButtonItem(title: "Continue", style: .Plain, target: self, action:"sayHello")

Frazil

you pass selectors in swift by just putting the selector in a string, action: "sayHello" – Celery

Thank you so much. I'm under pressure to get this out and was getting frustrated. – Frazil

This question was previously marked as a duplicate of @selector() in Swift?. However, this question asks specifically about UIBarButtonItem while the other does not. Requiring beginners to generalize all uses of selector can be difficult for them, so I am removing the duplicate status so that people can keep this question up to date. – Bearce

Answer 1

As of Swift 2.2, there is a special syntax for compiler-time checked selectors. It uses the syntax: #selector(methodName).

Swift 3 and later:

var b = UIBarButtonItem(
    title: "Continue",
    style: .plain,
    target: self,
    action: #selector(sayHello(sender:))
)

func sayHello(sender: UIBarButtonItem) {
}

If you are unsure what the method name should look like, there is a special version of the copy command that is very helpful. Put your cursor somewhere in the base method name (e.g. sayHello) and press Shift+Control+Option+C. That puts the ‘Symbol Name’ on your keyboard to be pasted. If you also hold Command it will copy the ‘Qualified Symbol Name’ which will include the type as well.

Swift 2.3:

var b = UIBarButtonItem(
    title: "Continue",
    style: .Plain,
    target: self,
    action: #selector(sayHello(_:))
)

func sayHello(sender: UIBarButtonItem) {
}

This is because the first parameter name is not required in Swift 2.3 when making a method call.

You can learn more about the syntax on swift.org here: https://swift.org/blog/swift-2-2-new-features/#compile-time-checked-selectors

Ronnieronny

Just to mention that the action function cannot be private! I am not really sure why, but I always get an error in case I provided the name of some private function – Humpback

I got this: "does not implement methodSignatureForSelector" – Statistical

@Statistical If you're using the 2nd version with the colon, you'll need to make sure the function parameter types match that for whatever action you're handling. – Touter

I was putting Selector("sayHello"). Good to know I can just put the String – Mandola

@RyanForsyth The string actually gets translated into Selector("sayHello") behind the scenes by Swift anyway. – Cordula

This answer is outdated. – Enwomb

I would recommend just including the most up to date answer. People can check the edit history if they want to know what your outdated answers were. The many different answers here make it hard to sort out. – Bearce

Answer 2

Swift 4/5 example

button.target = self
button.action = #selector(buttonClicked(sender:))

@objc func buttonClicked(sender: UIBarButtonItem) {
        
}

Huskey

This is right, for Swift 4 you need to add @objc to the function declaration. Up until Swift 4 this was implicitly inferred. – Aggappora

button.target = self – Enterostomy

@Mahesh don't need to set the target – Huskey

@Huskey target is needed for Swift 5 – Liquidize

Answer 3

Swift 5 & iOS 13+ Programmatic Example

1. You must mark your function with @objc, see below example!
2. No parenthesis following after the function name! Just use #selector(name).
3. private or public doesn't matter; you can use private.

Code Example

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    
    let menuButtonImage = UIImage(systemName: "flame")
    let menuButton = UIBarButtonItem(image: menuButtonImage, style: .plain, target: self, action: #selector(didTapMenuButton))
    navigationItem.rightBarButtonItem = menuButton
}

@objc public func didTapMenuButton() {
    print("Hello World")
}

Economy

Answer 4

May this one help a little more

Let suppose if you want to make the bar button in a separate file(for modular approach) and want to give selector back to your viewcontroller, you can do like this :-

your Utility File

class GeneralUtility {

    class func customeNavigationBar(viewController: UIViewController,title:String){
        let add = UIBarButtonItem(title: "Play", style: .plain, target: viewController, action: #selector(SuperViewController.buttonClicked(sender:)));  
      viewController.navigationController?.navigationBar.topItem?.rightBarButtonItems = [add];
    }
}

Then make a SuperviewController class and define the same function on it.

class SuperViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
            // Do any additional setup after loading the view.
    }
    @objc func buttonClicked(sender: UIBarButtonItem) {

    }
}

and In our base viewController(which inherit your SuperviewController class) override the same function

import UIKit

class HomeViewController: SuperViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func viewWillAppear(_ animated: Bool) {
        GeneralUtility.customeNavigationBar(viewController: self,title:"Event");
    }

    @objc override func buttonClicked(sender: UIBarButtonItem) {
      print("button clicked")    
    } 
}

Now just inherit the SuperViewController in whichever class you want this barbutton.

Thanks for the read

Weisbrodt

Answer 5

Swift 5

if you have created UIBarButtonItem in Interface Builder and you connected outlet to item and want to bind selector programmatically.

Don't forget to set target and selector.

addAppointmentButton.action = #selector(moveToAddAppointment)
addAppointmentButton.target = self

@objc private func moveToAddAppointment() {
     self.presenter.goToCreateNewAppointment()
}

Enterostomy

Answer 6

If you don't want to use target/action using a #selector, you can use primaryAction since iOS 14:

// here you can set the title or a image for the UIBarButtonItem
let action = UIAction(title: "", image: UIImage(systemName: "list.dash")) { _ in
    // handler
    print("hello world")
}
        
let barButtonItem = UIBarButtonItem(title: nil,
                                    image: nil,
                                    primaryAction: action,
                                    menu: nil)

Malcah