UIView 方法 swizzling swift 3 [英] UIView method swizzling swift 3

问题描述

我正在尝试根据答案在 swift 3 中实现方法 swizzling 如何在 Swift 3.0 中实现方法 swizzling?

I'm trying to implement method swizzling in swift 3 basing on answer How to implement method swizzling swift 3.0?

这是我的代码:

// MARK: - Swizzling

private let swizzling: (UIView.Type) -> () = { view in
    let originalSelector = #selector(view.awakeFromNib)
    let swizzledSelector = #selector(view.swizzled_localization_awakeFromNib)

    let originalMethod = class_getInstanceMethod(view, originalSelector)
    let swizzledMethod = class_getInstanceMethod(view, swizzledSelector)

    method_exchangeImplementations(originalMethod, swizzledMethod)
}

extension UIView {

    open override class func initialize() {
        guard self === UIView.self else {
            return
        }

        swizzling(self)
    }

    func swizzled_localization_awakeFromNib() {
        swizzled_localization_awakeFromNib()

        if let localizableView = self as? Localizable {
            localizableView.localize()
        }
    }

}

但是在应用程序启动时它会崩溃:

But on app launch it crashes with reason:

'-[UINavigationController swizzled_localization_awakeFromNib]:无法识别的选择器发送到实例 0x7fc7c8820400'

'-[UINavigationController swizzled_localization_awakeFromNib]: unrecognized selector sent to instance 0x7fc7c8820400'

我不明白为什么 swizzled_localization_awakeFromNib 调用 UINavigationController.我在obj-c项目中使用了这个，请问是这个原因吗?它通过 dispatch_once 在 swift 2 中运行良好.

I can't figure out why swizzled_localization_awakeFromNib called on UINavigationController. I am using this in obj-c project, can it be the reason? It worked fine in swift 2 throught dispatch_once.

我尝试在 swizzling(self) 之前放置断点，它按预期在 UIView 上调用了一次.

I tried place breakpoint before swizzling(self), and it called once on UIView, as expected.

推荐答案

问题在于 awakeFromNib 是 NSObject 和不是 UIView.您的代码将 NSObject 方法与UIView的方法，调用原方法崩溃当在 UINavigationController 上调用 swizzled 方法时(或 NSObject 的任何其他子类，它不是 UIView 的子类).

The problem is that awakeFromNib is a method of NSObject and not of UIView. Your code swizzles the NSObject method with a method of UIView, and calling the original method crashes when the swizzled method is called on UINavigationController (or any other subclass of NSObject which is not a subclass of UIView).

解决方法是尝试添加 swizzled 方法首先是原始名称(如 http://nshipster.com/method-swizzling/ 中所述):

The solution is to try to add the swizzled method with the original name first (as described in http://nshipster.com/method-swizzling/):

private let swizzling: (UIView.Type) -> () = { view in
    let originalSelector = #selector(view.awakeFromNib)
    let swizzledSelector = #selector(view.swizzled_localization_awakeFromNib)

    let originalMethod = class_getInstanceMethod(view, originalSelector)
    let swizzledMethod = class_getInstanceMethod(view, swizzledSelector)

    let didAddMethod = class_addMethod(view, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))
    if didAddMethod {
        class_replaceMethod(view, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod))
    } else {
        method_exchangeImplementations(originalMethod, swizzledMethod)
    }
}

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