swift - Swizzling导致递归

Question

因此，当我尝试调整 UIImage 的 init(named:) 以便我可以使用图像名称设置可访问性标识符时，看起来，即使我正在调用 method_exchangeImplementation，我的混合方法 ftg_imageNamed(named name: String) 和 init(named:) 都调用我的混合方法:ftg_imageNamed(named name: String) 创建一个无限循环。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，您的调配看起来“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 的实例，其中 swizzled 方法 UIImage.ftg_imageNamed(named:) 返回 Void。原始方法和 swizzled 方法都应具有相同的参数和返回类型，实现可能会有所不同。

你应该考虑一个简单的扩展方法来实现你想要的而不是混合。

编辑

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

用作

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