Attach parameter to button.addTarget action in Swift

Question

I am trying to pass an extra parameter to the buttonClicked action, but cannot work out what the syntax should be in Swift.

button.addTarget(self, action: "buttonClicked:", forControlEvents: UIControlEvents.TouchUpInside)

Any my buttonClicked method:

func buttonClicked(sender:UIButton)
{
    println("hello")
}

Anyone any ideas?

Thanks for your help.

Refer to [this link](http://stackoverflow.com/a/39584022/898057) for a detailed answer and best practice — sheetal, Sep 20 '16 at 00:36
The question doesn't have a good answer because it already describes a problematic architecture. You don't need an extra parameter. The need for a n additional parameter is a problem in your architecture. — Sulthan, Dec 27 '16 at 11:00
`WARNING TO INTERNET: please check out my answer at the bottom` — Mr Heelis, Oct 25 '17 at 14:26
You can pass parameters in newer Swift versions by using `addAction`, which is much more flexible than `addTarget`, see example below — zzpaf, Jan 15 '23 at 01:55

score 191 · Accepted Answer · edited Mar 30 '18 at 08:55

191

You cannot pass custom parameters in addTarget:.One alternative is set the tag property of button and do work based on the tag.

button.tag = 5
button.addTarget(self, action: "buttonClicked:", 
    forControlEvents: UIControlEvents.TouchUpInside)

Or for Swift 2.2 and greater:

button.tag = 5
button.addTarget(self,action:#selector(buttonClicked),
    forControlEvents:.TouchUpInside)

Now do logic based on tag property

@objc func buttonClicked(sender:UIButton)
{
    if(sender.tag == 5){

        var abc = "argOne" //Do something for tag 5
    }
    print("hello")
}

edited Mar 30 '18 at 08:55

Mostafa Sultan

2,268
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answered Jul 17 '14 at 23:08

codester

36,891
10
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4

Hi, If i want to get indexPath or cell of button in tableView, is it possible? – NKurapati Jun 04 '15 at 10:10
1

Here's a hint: Don't make the method private. – OhadM Apr 10 '16 at 07:31
2

Seems like it's type only can be an `Int`. Nothing else. – scaryguy Aug 04 '16 at 22:29
2

what if I want to pass row and section together? – Yestay Muratov Nov 15 '16 at 06:33
4

just so you know, despite 118 upvotes (and counting) this is the wrong way to do this – Mr Heelis Jan 05 '18 at 09:54

score 86 · Answer 2 · edited Dec 29 '19 at 09:34

86

If you want to send additional parameters to the buttonClicked method, for example an indexPath or urlString, you can subclass the UIButton:

class SubclassedUIButton: UIButton {
    var indexPath: Int?
    var urlString: String?
}

Make sure to change the button's class in the identity inspector to subclassedUIButton. You can access the parameters inside the buttonClicked method using sender.indexPath or sender.urlString.

Note: If your button is inside a cell you can set the value of these additional parameters in the cellForRowAtIndexPath method (where the button is created).

edited Dec 29 '19 at 09:34

moonvader

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answered Oct 08 '15 at 02:09

uclagamer

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6

This was the only way that worked for me. But I'm curious, is this anti-pattern or not? – scaryguy Aug 05 '16 at 19:01
1

This is the best way, I think – Duy Hoang Jun 22 '18 at 04:33

Mr Heelis · Answer 3 · 2018-04-02T11:11:30.760

I appreciate everyone saying use tags, but really you need to extend the UIButton class and simply add the object there..

Tags are a hopeless way round this. Extend the UIButton like this (in Swift 4)

import UIKit
class PassableUIButton: UIButton{
    var params: Dictionary<String, Any>
    override init(frame: CGRect) {
        self.params = [:]
        super.init(frame: frame)
    }

    required init?(coder aDecoder: NSCoder) {
        self.params = [:]
        super.init(coder: aDecoder)
    }
}

then your call may be call (NOTE THE colon ":" in Selector(("webButtonTouched:")))

let webButton = PassableUIButton(frame: CGRect(x:310, y:40, width:40, height:40))
webButton.setTitle("Visit",for: .normal)
webButton.addTarget(self, action: #selector(YourViewController.webButtonTouched(_:)), for:.touchUpInside)
webButton.params["myvalue"] = "bob"

then finally catch it all here

@IBAction func webButtonTouched(_ sender: PassableUIButton) {
    print(sender.params["myvalue"] ?? "")
}

You do this one time and use it throughout your project (you can even make the child class have a generic "object" and put whatever you like into the button!). Or use the example above to put an inexhaustible number of key/string params into the button.. Really useful for including things like urls, confirm message methodology etc

As an aside, it's important that the SO community realise this there is an entire generation of bad practice being cut'n'paste round the internet by an alarming number of programmers who don't understand/haven't been taught/missed the point of the concept of object extensions

Can anyone comment whether this is the correct way to do this or not? — Eric33187, Jun 09 '21 at 02:40
@Eric33187 It's a correct and, moreover, cleaner object oriented approach. But using tags is a lazy in place solution. They both work, but using tags - smells — Roman, Sep 22 '21 at 09:42

score 10 · Answer 4 · edited Feb 22 '17 at 03:05

10

For Swift 3.0 you can use following

button.addTarget(self, action: #selector(YourViewController.YourMethodName(_:)), for:.touchUpInside)

func YourMethodName(_ sender : UIButton) {
    print(sender.tag)

}

edited Feb 22 '17 at 03:05

Tomas Sykora

470
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15

answered Dec 27 '16 at 12:30

MK_iOS

388
5
13

Lloyd Keijzer · Answer 5 · 2018-12-14T11:47:23.460

Swift 4.2

Result:

testButton.on(.touchUpInside) { (sender, event) in
    // You can use any reference initialized before the code block here
    // You can access self by adding [weak self] before (sender, event)
    // You can then either make self strong by using a guard statement or use a optional operator (?)
    print("user did press test button")
}

In the file UIButton+Events.swift I've created an extension method for UIButton that binds a UIControl.Event to a completion handler called EventHandler:

import UIKit

fileprivate var bindedEvents: [UIButton:EventBinder] = [:]

fileprivate class EventBinder {

    let event: UIControl.Event
    let button: UIButton
    let handler: UIButton.EventHandler
    let selector: Selector

    required init(
        _ event: UIControl.Event,
        on button: UIButton,
        withHandler handler: @escaping UIButton.EventHandler
    ) {
        self.event = event
        self.button = button
        self.handler = handler
        self.selector = #selector(performEvent(on:ofType:))
        button.addTarget(self, action: self.selector, for: event)
    }

    deinit {
        button.removeTarget(self, action: selector, for: event)
        if let index = bindedEvents.index(forKey: button) {
            bindedEvents.remove(at: index)
        }
    }
}

private extension EventBinder {

    @objc func performEvent(on sender: UIButton, ofType event: UIControl.Event) {
        handler(sender, event)
    }
}

extension UIButton {

    typealias EventHandler = (UIButton, UIControl.Event) -> Void

    func on(_ event: UIControl.Event, handler: @escaping EventHandler) {
        bindedEvents[self] = EventBinder(event, on: self, withHandler: handler)
    }
}

The reason why I used a custom class for binding the event is to be able to dispose the reference later when the button is deintialised. This will prevent a possible memory leak from occurring. This wasn't possible within the UIButton its extension, because I'm not allowed to implement a property nor the deinit method.

score 2 · Answer 6 · edited Mar 30 '18 at 09:53

If you have a loop of buttons like me you can try something like this

var buttonTags:[Int:String]? // can be [Int:Any]
let myArray = [0:"a",1:"b"]
for (index,value) in myArray {

     let button = // Create a button

     buttonTags?[index] = myArray[index]
     button.tag = index
     button.addTarget(self, action: #selector(buttonAction(_:)), for: .touchDown)

}
@objc func buttonAction(_ sender:UIButton) {

    let myString = buttonTags[sender.tag]

}

Karsten · Answer 7 · 2018-06-06T07:34:35.603

2

Swift 4.0 code (Here we go again)

The called action should marked like this because that is the syntax for swift function for exporting functions into objective c language.

@objc func deleteAction(sender: UIButton) {
}

create some working button:

let deleteButton = UIButton(type: .roundedRect)
deleteButton.setTitle("Delete", for: [])
deleteButton.addTarget(self, action: #selector( 
MyController.deleteAction(sender:)), for: .touchUpInside)

edited Jun 06 '18 at 07:34

answered Oct 17 '17 at 11:21

Karsten

1,869
22
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Thanks for sharing. This works, but marking it with @objc feels unintuitive. Can you explain the reasoning for this? – rawbee Nov 14 '17 at 15:39
@rawbee Agree that this is counterintuitive. This question has more background: https://stackoverflow.com/questions/44390378/how-can-i-deal-with-objc-inference-deprecation-with-selector-in-swift-4?answertab=active#tab-top – Mikrasya Jun 09 '18 at 21:50

score 2 · Answer 8 · answered Apr 17 '19 at 23:55

Swift 5.0 code

I use theButton.tag but if i have plenty type of option, its be very long switch case.

theButton.addTarget(self, action: #selector(theFunc), for: .touchUpInside) 
theButton.frame.name = "myParameter"

.

@objc func theFunc(sender:UIButton){ 
print(sender.frame.name)
}

score 2 · Answer 9 · answered Jan 10 '20 at 17:19

This is more of an important comment. Sharing references of sytanx that is acceptable out of the box. For hack solutions look at other answers.

Per Apple's docs, Action Method Definitions have to be either one of these three. Anything else is unaccepted.

@IBAction func doSomething()
@IBAction func doSomething(sender: UIButton)
@IBAction func doSomething(sender: UIButton, forEvent event: UIEvent)

score 0 · Answer 10 · answered Sep 13 '16 at 13:27

0

For Swift 2.X and above

button.addTarget(self,action:#selector(YourControllerName.buttonClicked(_:)),
                         forControlEvents:.TouchUpInside)

answered Sep 13 '16 at 13:27

Dheeraj D

4,386
4
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score 0 · Answer 11 · answered Mar 23 '17 at 11:14

Swift 3.0 code

self.timer = Timer.scheduledTimer(timeInterval: timeInterval, target: self, selector:#selector(fetchAutocompletePlaces(timer:)), userInfo:[textView.text], repeats: true)

func fetchAutocompletePlaces(timer : Timer) {

  let keyword = timer.userInfo
}

You can send value in 'userinfo' and use that as parameter in the function.

score 0 · Answer 12 · answered Jun 13 '22 at 14:34

0

button.tag = indexPath.row
button.addTarget(self, action: "buttonClicked:", 
    forControlEvents: UIControlEvents.TouchUpInside)
cell.accessoryView = button;

Button tag may help you to retrieve dedicated records from the array/dictionary

answered Jun 13 '22 at 14:34

Narendra G

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4
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zzpaf · Answer 13 · 2023-01-15T01:51:10.047

Although you can not pass a parameter the way you propose (With addTarget), you can use the addAction, where you can call any other function with any parameters you want:

let btnAuto = UIButton(type: .system)
    btnAuto.frame = CGRect(x:0, y:0 , width:200, height:20)
    btnAuto.backgroundColor = .blue
    btnAuto.addAction(
        UIAction { _ in
            print("This gets printed when the button is pressed")
            dothis(param1, param2)
        }, for: .touchUpInside)
    self.view.addSubview(btnAuto)

This is specially useful when you programmatically create a series of buttons and you want each of them to do a different action.

iOS 14.0 or greater is required for this solution – pw2 May 15 '23 at 10:36 — pw2, May 15 '23 at 10:36

score -1 · Answer 14 · answered Oct 01 '22 at 20:10

May be overkill, but couldn't you use a protocol for this? Then there would really be no need to pass in a parameter because you should have access to the properties within the conforming class.

protocol ButtonActionDelegate {
      func buttonClicked()
}

class SomeClassWithSomeButton: ButtonActionDelegate {
      let button = UIButton
      button.addTarget(self, action: "buttonClicked", forControlEvents: UIControlEvents.TouchUpInside)

      func buttonClicked() {
           //Do specific action
          }
}

Attach parameter to button.addTarget action in Swift

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