Swizzling.swift

private let swizzling: (AnyClass, Selector, Selector) -> () = { forClass, originalSelector, swizzledSelector in
    let originalMethod = class_getInstanceMethod(forClass, originalSelector)
    let swizzledMethod = class_getInstanceMethod(forClass, swizzledSelector)
    method_exchangeImplementations(originalMethod, swizzledMethod)
}

extension UIView {

    open override class func initialize() {
        // make sure this isn't a subclass
        guard self === UIView.self else { return }

        let originalSelector = #selector(layoutSubviews)
        let swizzledSelector = #selector(swizzled_layoutSubviews)
        swizzling(self, originalSelector, swizzledSelector)
    }

    func swizzled_layoutSubviews() {
        swizzled_layoutSubviews()
        print("swizzled_layoutSubviews")
    }

}