swift - Can I extend viewWillAppear in UIViewController? -

i looking way extend implementation of function viewwillappear uiviewcontroller class make print class name of view called everytime function called.

i know it's not possible override functions in extensions wonder if there way this.

ok, after finding http://nshipster.com/swift-objc-runtime/ tried similar , achieve desired result.

the code looks like:

extension uiviewcontroller { public override class func initialize() {     struct static {         static var token: dispatch_once_t = 0     }      // make sure isn't subclass     if self !== uiviewcontroller.self {         return     }      dispatch_once(&static.token) {         let originalselector = #selector(uiviewcontroller.viewwillappear(_:))         let swizzledselector = #selector(uiviewcontroller.nsh_viewwillappear(_:))          let originalmethod = class_getinstancemethod(self, originalselector)         let swizzledmethod = class_getinstancemethod(self, swizzledselector)          let didaddmethod = class_addmethod(self, originalselector, method_getimplementation(swizzledmethod), method_gettypeencoding(swizzledmethod))          if didaddmethod {             class_replacemethod(self, swizzledselector, method_getimplementation(originalmethod), method_gettypeencoding(originalmethod))         } else {             method_exchangeimplementations(originalmethod, swizzledmethod)         }     } }  // mark: - method swizzling  func nsh_viewwillappear(animated: bool) {     self.nsh_viewwillappear(animated)     nslog("viewwillappear: \(self)") } }