swift4.0 runtime 方法替换

https://www.jianshu.com/p/a6b675f4d073

+(void)load 方法已经失效
swift3.0 中的 initialize 也失效

网络收集来的代码，做记录

extension UIViewController {

public class func initializeMethod() {
    
    let originalSelector = #selector(UIViewController.viewDidAppear(_:))
    let swizzledSelector = #selector(UIViewController.myMethod(animated:))
    
    let originalMethod = class_getInstanceMethod(self, originalSelector)
    let swizzledMethod = class_getInstanceMethod(self, swizzledSelector)
    
    
    //在进行 Swizzling 的时候,需要用 class_addMethod 先进行判断一下原有类中是否有要替换方法的实现
    let didAddMethod: Bool = class_addMethod(self, originalSelector, method_getImplementation(swizzledMethod!), method_getTypeEncoding(swizzledMethod!))
    //如果 class_addMethod 返回 yes,说明当前类中没有要替换方法的实现,所以需要在父类中查找,这时候就用到 method_getImplemetation 去获取 class_getInstanceMethod 里面的方法实现,然后再进行 class_replaceMethod 来实现 Swizzing
    
    if didAddMethod {
        class_replaceMethod(self, swizzledSelector, method_getImplementation(originalMethod!), method_getTypeEncoding(originalMethod!))
    } else {
        method_exchangeImplementations(originalMethod!, swizzledMethod!)
    }
    
    
}

@objc func myMethod(animated: Bool) {
    self.myMethod(animated: animated)  
}