问题描述
在 Swift 中，您可以像这样为按钮创建一个函数:
In Swift you can create a function for a button like this:
button.addTarget(self, action: #selector(buttonAction), forControlEvents: .TouchUpInside)
但是有办法让我做这样的事情:
However is there a way I can do something like this:
button.whenButtonIsClicked({Insert code here})
这样我什至没有为按钮声明一个显式函数.我知道我可以使用按钮标签，但我更愿意这样做.
That way I do not even have too declare an explicit function for the button. I know I can use button tags but I would prefer to do this instead.
推荐答案
创建你自己的 UIButton 子类来做到这一点:
Create your own UIButton subclass to do this:
class MyButton: UIButton {
var action: (() -> Void)?
func whenButtonIsClicked(action: @escaping () -> Void) {
self.action = action
self.addTarget(self, action: #selector(MyButton.clicked), for: .touchUpInside)
}
// Button Event Handler:
// I have not marked this as @IBAction because it is not intended to
// be hooked up to Interface Builder
@objc func clicked() {
action?()
}
}
当您以编程方式创建按钮然后调用 whenButtonIsClicked 来设置其功能时，用 MyButton 替换 UIButton.
Substitute MyButton for UIButton when you create buttons programmatically and then call whenButtonIsClicked to set up its functionality.
您也可以在情节提要中将其与 UIButton 一起使用(只需将其类更改为 MyButton)，然后在 中调用 .whenButtonIsClicked>viewDidLoad
You can also use this with UIButtons in a Storyboard (just change their class to MyButton) and then call whenButtonIsClicked in viewDidLoad.
@IBOutlet weak var theButton: MyButton!
var count = 0
override func viewDidLoad() {
super.viewDidLoad()
// be sure to declare [unowned self] if you access
// properties or methods of the class so that you
// don't create a strong reference cycle
theButton.whenButtonIsClicked { [unowned self] in
self.count += 1
print("count = (self.count)")
}
更强大的实现
认识到程序员可能想要处理更多事件而不仅仅是 .touchUpInside，我编写了这个功能更强大的版本，它支持每个 UIButton 多个闭包和每个事件多个闭包输入.
Recognizing the fact that programmers might want to handle more events than just .touchUpInside, I wrote this more capable version which supports multiple closures per UIButton and multiple closures per event type.
class ClosureButton: UIButton {
private var actions = [UInt : [((UIControl.Event) -> Void)]]()
private let funcDict: [UInt : Selector] = [
UIControl.Event.touchCancel.rawValue: #selector(eventTouchCancel),
UIControl.Event.touchDown.rawValue: #selector(eventTouchDown),
UIControl.Event.touchDownRepeat.rawValue: #selector(eventTouchDownRepeat),
UIControl.Event.touchUpInside.rawValue: #selector(eventTouchUpInside),
UIControl.Event.touchUpOutside.rawValue: #selector(eventTouchUpOutside),
UIControl.Event.touchDragEnter.rawValue: #selector(eventTouchDragEnter),
UIControl.Event.touchDragExit.rawValue: #selector(eventTouchDragExit),
UIControl.Event.touchDragInside.rawValue: #selector(eventTouchDragInside),
UIControl.Event.touchDragOutside.rawValue: #selector(eventTouchDragOutside)
]
func handle(events: [UIControl.Event], action: @escaping (UIControl.Event) -> Void) {
for event in events {
if var closures = actions[event.rawValue] {
closures.append(action)
actions[event.rawValue] = closures
} else {
guard let sel = funcDict[event.rawValue] else { continue }
self.addTarget(self, action: sel, for: event)
actions[event.rawValue] = [action]
}
}
}
private func callActions(for event: UIControl.Event) {
guard let actions = actions[event.rawValue] else { return }
for action in actions {
action(event)
}
}
@objc private func eventTouchCancel() { callActions(for: .touchCancel) }
@objc private func eventTouchDown() { callActions(for: .touchDown) }
@objc private func eventTouchDownRepeat() { callActions(for: .touchDownRepeat) }
@objc private func eventTouchUpInside() { callActions(for: .touchUpInside) }
@objc private func eventTouchUpOutside() { callActions(for: .touchUpOutside) }
@objc private func eventTouchDragEnter() { callActions(for: .touchDragEnter) }
@objc private func eventTouchDragExit() { callActions(for: .touchDragExit) }
@objc private func eventTouchDragInside() { callActions(for: .touchDragInside) }
@objc private func eventTouchDragOutside() { callActions(for: .touchDragOutside) }
}
演示
class ViewController: UIViewController {
var count = 0
override func viewDidLoad() {
super.viewDidLoad()
let button = ClosureButton(frame: CGRect(x: 50, y: 100, width: 60, height: 40))
button.setTitle("press me", for: .normal)
button.setTitleColor(.blue, for: .normal)
// Demonstration of handling a single UIControl.Event type.
// If your closure accesses self, be sure to declare [unowned self]
// to prevent a strong reference cycle
button.handle(events: [.touchUpInside]) { [unowned self] _ in
self.count += 1
print("count = (self.count)")
}
// Define a second handler for touchUpInside:
button.handle(events: [.touchUpInside]) { _ in
print("I'll be called on touchUpInside too")
}
let manyEvents: [UIControl.Event] = [.touchCancel, .touchUpInside, .touchDown, .touchDownRepeat, .touchUpOutside, .touchDragEnter,
.touchDragExit, .touchDragInside, .touchDragOutside]
// Demonstration of handling multiple events
button.handle(events: manyEvents) { event in
switch event {
case .touchCancel:
print("touchCancel")
case .touchDown:
print("touchDown")
case .touchDownRepeat:
print("touchDownRepeat")
case .touchUpInside:
print("touchUpInside")
case .touchUpOutside:
print("touchUpOutside")
case .touchDragEnter:
print("touchDragEnter")
case .touchDragExit:
print("touchDragExit")
case .touchDragInside:
print("touchDragInside")
case .touchDragOutside:
print("touchDragOutside")
default:
break
}
}
self.view.addSubview(button)
}
}
这篇关于Swift 以编程方式为带有闭包的按钮创建函数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！