ios - 在 Swift 中使用 Bool 的 View Controller 扩展

Question

我正在尝试对 View Controller 进行扩展。这是带有点击识别器的简单 View 。如果按下一次，背景颜色应该从品红色变为橙色。到下一次推送时，它应该再次变成洋红色。

如果我为具体的 VC 做这件事，比方说 StartVC，它就可以工作。这是代码:

import UIKit

class StartVC: UIViewController {
    // bool
    var colorChanged = false

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor.magenta
        setMyTouchableView2()
    }
}

extension StartVC {
    // make touchable view
    func setMyTouchableView2() {
        let myView = UIImageView(frame: CGRect(x: 100, y: 100, width: 50, height: 50))
        myView.backgroundColor = UIColor.yellow

        // add gesture recognizer
        let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(changeColor2(_:)))
        myView.addGestureRecognizer(tapGestureRecognizer)
        myView.isUserInteractionEnabled = true

        view.addSubview(myView)
    }

    func changeColor2(_ recognizer:UITapGestureRecognizer){
        if(colorChanged) {
            view.backgroundColor = UIColor.magenta
        } else {
            view.backgroundColor = UIColor.orange
        }

        colorChanged = !colorChanged
    }
}

但是如果我尝试将此扩展推广到任何 View Controller ，我会遇到以下问题:我无法将我的 boolean 值 (colorChanged) 放入 View Controller 中，因为扩展看不到它。我该如何解决？

代码如下:

import UIKit

class ViewController: UIViewController {
    // bool
    var colorChanged = false

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor.magenta
        setMyTouchableView()
    }
}

extension UIViewController {
    // make touchable view
    func setMyTouchableView() {
        let myView = UIImageView(frame: CGRect(x: 100, y: 100, width: 50, height: 50))
        myView.backgroundColor = UIColor.yellow

        // add gesture recognizer
        let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(changeColor(_:)))
        myView.addGestureRecognizer(tapGestureRecognizer)
        myView.isUserInteractionEnabled = true

        view.addSubview(myView)
    }

    func changeColor(_ recognizer:UITapGestureRecognizer){
        if(colorChanged) {
            view.backgroundColor = UIColor.magenta
        } else {
            view.backgroundColor = UIColor.orange
        }
    }

Answer 1

扩展默认不能有存储属性。但是，如果你真的需要它，你可以通过 objc runtime 创建它

private var associationKey: UInt8 = 111 // Some constant

extension ViewController {
    var colorChanged: Bool {
        get {
            return objc_getAssociatedObject(self, &associationKey) as! Bool
        }
        set {
            objc_setAssociatedObject(self, &associationKey, newValue, .OBJC_ASSOCIATION_ASSIGN)
        }
    }
}

但是您可能会遇到一个问题，即多个 Controller 会更改此标志。所以你也可以尝试使用协议(protocol)

protocol ColorChangable {
    var colorChange: Bool { get set }
}

extension ColorChangable where Self: UIViewController {
    func setMyTouchableView {
        // Your logic
    }
}

class ViewController: UIViewController {
    var colorChange: Bool

    func viewDidLoad() {
        self.viewDidLoad()

        setMyTouchableView()
    }
}

extension ViewController: ColorChangable {}