ios - 如何使用 Swift 4/5 扩展多个类

Question

我正在尝试扩展多个类，它们是 UIButton 和 UITextField。它们都具有相同的功能，当我调用该函数时它们可以摆动。我尽量不重复我的代码一次以上。我一直在尝试使用可以扩展和编写我想要的函数的协议(protocol)，然后在我的类中扩展它们，但问题出在我的函数中，我必须调用 self，但我会得到一个错误，因为 self 可以是仅在 UITextField 和 UIButton 上调用。

这是我的代码

import UIKit

extension UIButton {

    func wiggle() {
        let position = "position"
        let wiggleAnimation = CABasicAnimation(keyPath: position)
        wiggleAnimation.duration = 0.05
        wiggleAnimation.repeatCount = 5
        wiggleAnimation.autoreverses = true
        wiggleAnimation.fromValue = CGPoint(x: self.center.x - 4.0, y: self.center.y)
        wiggleAnimation.toValue = CGPoint(x: self.center.x + 4.0, y: self.center.y)
        layer.add(wiggleAnimation, forKey: position)
    }

}

extension UITextField {

    func wiggle() {
        let position = "position"
        let wiggleAnimation = CABasicAnimation(keyPath: position)
        wiggleAnimation.duration = 0.05
        wiggleAnimation.repeatCount = 5
        wiggleAnimation.autoreverses = true
        wiggleAnimation.fromValue = CGPoint(x: self.center.x - 4.0, y: self.center.y)
        wiggleAnimation.toValue = CGPoint(x: self.center.x + 4.0, y: self.center.y)
        layer.add(wiggleAnimation, forKey: position)
    }

}

这是我尝试过的尝试，但由于我正在调用 self，所以出现错误。

protocol Animations {
    func wiggle()
}

extension Animations {
    func wiggle() {
        let position = "position"
        let wiggleAnimation = CABasicAnimation(keyPath: position)
        wiggleAnimation.duration = 0.05
        wiggleAnimation.repeatCount = 5
        wiggleAnimation.autoreverses = true
        wiggleAnimation.fromValue = CGPoint(x: self.center.x - 4.0, y: self.center.y)
        wiggleAnimation.toValue = CGPoint(x: self.center.x + 4.0, y: self.center.y)
        layer.add(wiggleAnimation, forKey: position)
    }
}

extension UIButton: Animations {}

extension UITextField: Animations {}

我收到的错误是“Self”类型的值没有成员“center”“Self”类型的值没有成员“center”使用未解析的标识符“层”

Answer 1

只有 UIView 有 center 属性。对于 Swift 5+，您的协议(protocol)声明应如下所示:

protocol Animations: UIView {
    func wiggle()
}

注意只有 UIViews 可以符合这个协议(protocol)。

对于 Swift 4.x，你必须像这样使用它:

protocol Animations {
    func wiggle()
}

extension Animations where Self: UIView {
   func wiggle() {
        let position = "position"
        let wiggleAnimation = CABasicAnimation(keyPath: position)
        wiggleAnimation.duration = 0.05
        wiggleAnimation.repeatCount = 5
        wiggleAnimation.autoreverses = true
        wiggleAnimation.fromValue = CGPoint(x: self.center.x - 4.0, y: self.center.y)
        wiggleAnimation.toValue = CGPoint(x: self.center.x + 4.0, y: self.center.y)
        layer.add(wiggleAnimation, forKey: position)
    }
}