IOS Swift handle global events

问题

How can I handle global events triggered by the notification centre for example in my API class I fire an event if an error response is received e.g. (500). When that event is fired an UIAlert should be displayed on what ever view controller is active, or on logout the login view controller should be presented.

As far as I can see there is no easy way to get the current view controller in order to interact with it. (Note that my root view controller is NOT a navigation controller).

回答1:

Is this way too hard to get current view controller ( when not using navigation controller ) ?

// on your app delegate    
getCurrentViewController(self.window!.rootViewController!)

func getCurrentViewController(viewController:UIViewController)-> UIViewController{

    if let navigationController = viewController as? UINavigationController{
       return getCurrentViewController(navigationController.visibleViewController)
    }

    if let viewController = viewController?.presentedViewController {

        return getCurrentViewController(viewController)

    }else{

        return viewController
    }
}

回答2:

An alternative solution, that will work regardless of whether your view controllers are embedded in a UINavigationController or not, would be to subclass UIViewController. This class will handle receiving the NSNotification that an error occurred and will also handle displaying the alert:

class MyViewController: UIViewController {
    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)
        NSNotificationCenter.defaultCenter().addObserver(self,
                                             selector: "errorOccured",
                                             name: "ErrorNotification",
                                             object: nil)
    }

    override func viewWillDisappear(animated: Bool) {
        super.viewWillDisappear(animated)
        NSNotificationCenter.defaultCenter().removeObserver(self, name: "ErrorNotification", object: nil)
    }

    func errorOccured() {
        // Present an UIAlertViewController or the login screen.
    }
}

Now, any UIViewControllers that should display an alert when the error notification is posted just have to be a subclass of MyViewController. Just make sure, if you override viewWillAppear or viewWillDisappear, that you call super.viewWillAppear or super.viewWillDisappear.

回答3:

For BroadCast Notification

NSNotificationCenter.defaultCenter().postNotificationName("erro400", object: nil)

For Receive

override func viewWillAppear(animated: Bool) {
NSNotificationCenter.defaultCenter().addObserver(self, selector: "ErroOccure", name: "erro400", object: nil)
}

func ErroOccure()
{
    //present alert from here
   // do whatever you want
}

You have to Remove Notification when you finish with it.

override func viewWillDisappear(animated: Bool) {
    NSNotificationCenter.defaultCenter().removeObserver(self)
}

来源：https://stackoverflow.com/questions/30618361/ios-swift-handle-global-events

标签

ios

swift

cocoa-touch

events