导致递归的Swizzling

Question

因此，当我尝试使用UIImage的init(named:)来设置可访问性标识符时，尽管我调用的是method_exchangeImplementation，但我的混合方法ftg_imageNamed(named name: String)和init(named:)似乎都调用了我的混合方法：ftg_imageNamed(named name: String)，创建了一个无限循环。这是为什么？

调用method_exchangeImplementation

extension UIImage {

    static func swizzleInitImplementation() {
        let originalSelector =  #selector(UIImage.init(named:))
        let swizzledSelector = #selector(UIImage.ftg_imageNamed(named:))


        let imgSelf: AnyClass = self.classForCoder()

        guard  let originalMethod = class_getClassMethod(imgSelf, originalSelector),
            let swizzledMethod = class_getClassMethod(imgSelf, swizzledSelector) else {
                assertionFailure("The methodsw are not found")
                return
        }

        method_exchangeImplementations(originalMethod, swizzledMethod)
    }

    @objc static func ftg_imageNamed(named name: String)  {
        setAccessibilityLabel(name)
        self.ftg_imageNamed(named: name)
    }

}

以同样的方式失败的手动实现。

extension UIImage {

    static func swizzleInitImplementation() {
        let originalSelector =  #selector(UIImage.init(named:))
        let swizzledSelector = #selector(UIImage.ftg_imageNamed(named:))


        let imgSelf: AnyClass = self.classForCoder()

        guard  let originalMethod = class_getClassMethod(imgSelf, originalSelector),
            let swizzledMethod = class_getClassMethod(imgSelf, swizzledSelector) else {
                assertionFailure("The methodsw are not found")
                return
        }

        let imp1 = method_getImplementation(originalMethod)
        let imp2 = method_getImplementation(swizzledMethod)
        method_setImplementation(originalMethod, imp2)
        method_setImplementation(swizzledMethod, imp1)

    }

    @objc static func ftg_imageNamed(named name: String)  {
        setAccessibilityLabel(name)
        self.ftg_imageNamed(named: name)
    }

}

Answer 1

在self.UI(named: name)之前，你的声音似乎是"ok“。因此请检查该方法是否存在无限循环问题。

现在，这是一个糟糕的swizzling实现。UIImage.init(named:)返回UIImage的一个实例，而swizzled方法UIImage.ftg_imageNamed(named:)返回Void。原始方法和swizzled方法应该具有相同的参数和返回类型，实现方式可能会有所不同。

你应该考虑一种简单的扩展方法来实现你想要的，而不是混乱。

编辑

extension UIImage {
    static func initIncludingAccessibility(named: String) -> UIImage {
       let img = UIImage(named: named)
       img.setAccessibilityLabel(named)
       return img
    }
}

将其用作

let image = UIImage.initIncludingAccessibility(named: /* your_image_name*/)