Adding a closure as target to a UIButton

Question

I have a generic control class which needs to set the completion of the button depending on the view controller.Due to that setLeftButtonActionWithClosure function needs to take as parameter a closure which should be set as action to an unbutton.How would it be possible in Swift since we need to pass the function name as String to action: parameter.

func setLeftButtonActionWithClosure(completion: () -> Void)
{
    self.leftButton.addTarget(<#target: AnyObject?#>, action: <#Selector#>, forControlEvents: <#UIControlEvents#>)
}

Answer 1

Do Not Use This Answer, See Note Below

NOTE: like @EthanHuang said "This solution doesn't work if you have more than two instances. All actions will be overwrite by the last assignment." Keep in mind this when you develop, i will post another solution soon.

If you want to add a closure as target to a UIButton, you must add a function to UIButton class by using extension

Swift 5

import UIKit    
extension UIButton {
    private func actionHandler(action:(() -> Void)? = nil) {
        struct __ { static var action :(() -> Void)? }
        if action != nil { __.action = action }
        else { __.action?() }
    }   
    @objc private func triggerActionHandler() {
        self.actionHandler()
    }   
    func actionHandler(controlEvents control :UIControl.Event, ForAction action:@escaping () -> Void) {
        self.actionHandler(action: action)
        self.addTarget(self, action: #selector(triggerActionHandler), for: control)
    }
}

Older

import UIKit

extension UIButton {
    private func actionHandleBlock(action:(() -> Void)? = nil) {
        struct __ {
            static var action :(() -> Void)?
        }
        if action != nil {
            __.action = action
        } else {
            __.action?()
        }
    }
    
    @objc private func triggerActionHandleBlock() {
        self.actionHandleBlock()
    }
    
    func actionHandle(controlEvents control :UIControlEvents, ForAction action:() -> Void) {
        self.actionHandleBlock(action)
        self.addTarget(self, action: "triggerActionHandleBlock", forControlEvents: control)
    }
}

and the call:

 let button = UIButton()
 button.actionHandle(controlEvents: .touchUpInside, 
 ForAction:{() -> Void in
     print("Touch")
 })