Easy closure based access to UIControl events (instead of target/action)

ControlEventBindable.swift

protocol ControlEventBindable: class { }

extension UIControl: ControlEventBindable { }
extension UIBarButtonItem: ControlEventBindable { }

private struct Keys {
    static var EventHandlers = "_EventHandlers"
}

// MARK: - Implementation
extension ControlEventBindable where Self: UIControl {
    private var eventHandlers: [ControlEventHandler<Self>] {
        get { return (objc_getAssociatedObject(self, &Keys.EventHandlers) as? [ControlEventHandler<Self>]) ?? [] }
        set { objc_setAssociatedObject(self, &Keys.EventHandlers, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC) }
    }

    /// Listen for `UIControlEvents` executing the provided closure when triggered
    func on(_ events: UIControlEvents, call closure: @escaping (Self) -> Void) {
        let handler = ControlEventHandler<Self>(sender: self, events: events, closure: closure)
        self.eventHandlers.append(handler)
    }
}
extension ControlEventBindable where Self: UIBarButtonItem {
    private var eventHandlers: [BarButtonItemEventHandler<Self>] {
        get { return (objc_getAssociatedObject(self, &Keys.EventHandlers) as? [BarButtonItemEventHandler<Self>]) ?? [] }
        set { objc_setAssociatedObject(self, &Keys.EventHandlers, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC) }
    }

    init(barButtonSystemItem: UIBarButtonSystemItem, closure: @escaping (Self) -> Void) {
        self.init(barButtonSystemItem: barButtonSystemItem, target: nil, action: nil)
        self.eventHandlers.append(BarButtonItemEventHandler<Self>(sender: self, closure: closure))
    }
    init(title: String?, style: UIBarButtonItemStyle, closure: @escaping (Self) -> Void) {
        self.init(title: title, style: style, target: nil, action: nil)
        self.eventHandlers.append(BarButtonItemEventHandler<Self>(sender: self, closure: closure))
    }
}

private final class ControlEventHandler<Sender: UIControl>: NSObject {
    let closure: (Sender) -> Void

    init(sender: Sender, events: UIControlEvents, closure: @escaping (Sender) -> Void) {
        self.closure = closure
        super.init()

        sender.addTarget(self, action: #selector(self.action), for: events)
    }

    @objc private func action(sender: UIControl) {
        guard let sender = sender as? Sender else { return }

        self.closure(sender)
    }
}
private final class BarButtonItemEventHandler<Sender: UIBarButtonItem>: NSObject {
    private let closure: (Sender) -> Void
    private let cleanup: () -> Void

    init(sender: Sender, closure: @escaping (Sender) -> Void) {
        self.closure = closure
        self.cleanup = {
            sender.target = nil
            sender.action = nil
        }

        super.init()

        sender.target = self
        sender.action = #selector(self.action)
    }
    deinit { cleanup() }

    @objc private func action(sender: UIBarButtonItem) {
        guard let sender = sender as? Sender else { return }

        self.closure(sender)
    }
}

Example.swift

let button = UIButton()

button.on(.touchUpInside) { button in
  //use button as a UIButton  
}

let barButtonItem = UIBarButtonItem(barButtonSystemItem: .cancel) { button in
  //use barbutton
}

LICENSE

MIT License

Copyright (c) [year] [fullname]

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

updated to include UIBarButtonItems