Send data back to rootviewcontroller before a popToRootViewController method call?

Question

What is the best way to send data back to the root view controller before calling the popToRootViewControllerAnimated method? I am trying to signal to the rootviewcontroller that the current viewcontroller no longer exists and keep a record of what viewcontroller has been pushed thru segue.

score 7 · Accepted Answer · answered Mar 05 '13 at 21:26

7

You mustn't wait until the current view controller "no longer exists". While the current view controller does exist, the root view controller is the current view controller's navigationController.viewControllers[0]. So you have the reference you need to send a message from this one to that one. Just cast to the root view controller's class and now you can call any public method in the root view controller, e.g.

MyRootViewController* rvc = (MyRootViewController*)(self.navigationController.viewControllers[0]);
rvc.coolData = myCoolData;

answered Mar 05 '13 at 21:26

matt

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By the way, the general problem of getting a reference from one object to another in iOS programming is discussed in my book, here: http://www.apeth.com/iOSBook/ch13.html#_instance_visibility – matt Mar 06 '13 at 06:03
Sounds good; thanks. Would you say this method is deemed appropriate in terms of Objective-C standards and the whole idea of OO? – David Mar 06 '13 at 19:28

score 2 · Answer 2 · edited May 23 '17 at 11:46

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There are two basic ways to do this: 1) with an NSNotification message or 2) with a delegate call. There are plenty of tutorials on how to code both. I wrote a small delegate tutorial as an answer to this question: Back button in iphone app and you can find a great NSNotification tutorial here: Send and receive messages through NSNotificationCenter in Objective-C?

edited May 23 '17 at 11:46

Community

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answered Mar 05 '13 at 21:20

JiuJitsuCoder

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score 1 · Answer 3 · answered Mar 05 '13 at 21:20

You can subclass UINavigationController and override the necessary methods to track your array. I would recommend keeping a uniqued set of titles for each view controller popped off the stack. As for signaling to the current view controller that the previous view controller doesn't exist, that's what -viewWillAppear is for. If you need finer-grain control, create a protocol for your View Controller instances to conform to that the navigation controller calls out to when it pops one or more of them off the stack.

Send data back to rootviewcontroller before a popToRootViewController method call?

3 Answers3