Swizzle `init` 并在内部调用实际实现，Swift 4

Question

我想调配 NSView 的 init(frame:) 但在里面调用真正的 init(frame:)。这可能吗？我知道，我可以通过子类化和重写来实现相同的目标，但是要在所有地方更改它会做太多工作。我不知道如何正确实现 swizzled 方法来避免递归。我的代码：

@objc func swizzledFrameInit(frame: NSRect) {
    //?? how to call init here
    self.wantsLayer = true
}


static func swizzleInitDescription() {
    DispatchQueue.once(token: "swizzleInitDescription") {
        let originalInitWithFrameSelector = #selector(NSView.init(frame:))

        let swizzledFrameSelector = #selector(NSView.swizzledFrameInit(frame:))

        let originalFrameInit = class_getInstanceMethod(self, originalInitWithFrameSelector)

        let swizzledFrameInit = class_getInstanceMethod(self, swizzledFrameSelector)

        let didAddSwizzledFrameInit = class_addMethod(self, originalInitWithFrameSelector, method_getImplementation(swizzledFrameInit!), method_getTypeEncoding(swizzledFrameInit!))

        if didAddSwizzledFrameInit {
            class_replaceMethod(self, swizzledFrameSelector, method_getImplementation(originalFrameInit!), method_getTypeEncoding(originalFrameInit!))
        } else {
            method_exchangeImplementations(originalFrameInit!, swizzledFramaInit!)
        }
    }
}

我也尝试了几乎相同的方法，但使用 convenience init 并得到了递归。任何帮助将不胜感激。

Answer 1

撇开如果用于探索和调试以外的任何事情，这是一个非常危险且不明智的调整，method_exchangeImplementations 的要点是它交换实现.这意味着旧的实现变成了 swizzled 方法。所以要调用你自己调用的旧实现：

@objc func swizzledFrameInit(frame: NSRect) {
    self.swizzledFrameInit(frame: frame)
    self.wantsLayer = true
}

一般来说，实现您在这里所做的事情的正确方法是在顶层视图上设置 wantsLayer。属性适用于所有子视图。

Creating a layer-backed view implicitly causes the entire view hierarchy under that view to become layer-backed. Thus, the view and all of its subviews (including subviews of subviews) become layer-backed

Swizzle `init` 并在内部调用实际实现，Swift 4

Swizzle `init` and invoke actual implementation inside, Swift 4

cocoa

swift

method-swizzling