I have a master/detail app and I'm displaying a modal from my my master view. My modal contains a navigation controller and two sub views. The first subview (login) pushes to the second subview (pick and initialize data). How do I get a reference to the second subview so I can catch it's delegate call in my master?
The goal is to update my master table view after the user logs in and initializes the core data database from a JSON webservice.
Thanks for any help!
When you say 'subview' I assume you mean the second viewController of your modally-presented navigationController's stack. If so you can't refer forward to it from your master view before you present as it is not yet created (the modal NavController is responsible for that).
You could refer to the first viewController - as
[[self presentedViewController] topViewController]
pass yourself as delegate to that controller, which would then be responsible for passing your delegate reference onwards to the second controller when it is created.
More simply though, you can refer back to the presenting setup from your second viewController thus:
[[self navigationController] presentingViewController]
This will get you to a reference to the container controller from where the presenting took place from where you can easily get a reference to the detail viewController.
You could use that route to get your data back to your master table view.
see also my answer here:
How can I pass value between NavigationController and ViewController with StoryBoard?
Related
in the viewDidLoad method i have this code.
When the application is running its not go to the another viewController, its gives me an error:
Warning: Attempt to present <CompleteCountryViewController: 0x7fb971779be0> on <ViewController: 0x7fb97176f3e0> whose view is not in the window hierarchy!
What can i do, that when the application running its will go to another viewController?
You should not present a view controller in the viewDidLoad method of another controller because you cannot show a view controller (present modally or push) when a transition is already occurring (push, pop, present, dismiss).
My suggestion is that you move the code in your code sample to the viewDidAppear: method. At this point, you know for sure that the transition has completed.
You seem to have a slight misunderstanding of the lifecycle of UIViewController if you want to modally present a view controller inside the viewDidLoad of another one.
viewDidLoad gets called in one view controller after it has been instantiated and its view components have been loaded (thus the name). The view of that view controller is about to be displayed, so it doesn't make much sense to instantiate another view controller at this point and present it on the first one.
Let me give you an example with two view controller A and B.
You instantiate A and its viewDidLoad gets called. So, A is about to be displayed! What you are doing in your code now is to instantiate B at this very point and show it on A. iOS doesn't like that and will give you your error.
I had an issue where I was attempting to present a modal view controller within the viewDidLoad method. The solution for me was to move this call to the viewDidAppear: method.
View controller's view is not in the window's view hierarchy at the point that it has been loaded (when the viewDidLoad message is sent), but it is in the window hierarchy after it has been presented (when the viewDidAppear: message is sent).
I'm working with three view contollers, the first called "menuVC" embedded in a navigation controller, and then "viewVC" and "resultsVC". I'm using push segues from VC to VC.
Now, my problem is, that every time I return to the first "menuVC" from the last "resultsVC", both viewDidLoad and viewDidAppear is envoked. As far as I can read everywhere, a navigation controller scene with push segues will never "pop" the rootviewcontroller, or any view controller for that matter, when I use push segues...? Or is there something I'm missing?
So, my question is - why is my first view controller "MenuVC" loading a new instance every time, when I should actually just be returning to the same instance of the "MenuVC"?
it depends on how to came back to the rootview controller from the last view controller.
you should better use
UIViewController *vc=[nav viewControllers].lastObject;
[vc.navigationController popToRootViewControllerAnimated:FALSE];
I perform some data loading tasks from an Ojective§C class and once everything is loaded, I simply wants to display a Viewcontroller subclass prepared in a storyboard.
So when everything is ok, the following method is called:
- (void)loadingNextView
{
CABBndGSite *mySite = [CABBndGSite alloc];
CABBndGSelectLanguageViewController *vc = [[mySite myRootViewController].storyboard instantiateViewControllerWithIdentifier:#"SelectLanguageViewController"];
[[mySite myRootViewController] presentViewController:vc animated:YES completion:nil];
}
So I verified that myRootViewController is not nil. It's a UINavigationController class.
vc is not nil so it found my view in the storyboard.
Anyway, the presentViewcontroller message seems to doing what expected.
Certainly a stupid mistake but my poor iOS programming knowledge lets me in the fog!
I use this code from ViewController subclasses with success and as here I get a valid ViewController pointer, I don't understand why it doesn't work.
I also tried to implement the AppDelegate method explained here How to launch a ViewController from a Non ViewController class? but I get a nil navigation pointer. Maybe something not well connected in my application
May I have some explanation?
Kind regards,
UINavigationController maintains a stack of view controllers. You can access this stack through the viewControllers property. To present your view controller, you can:
(a) have the navigation controller push the new view controller on to
the stack (pushViewController:animated:);
(b) have the top view controller in the view controller stack present
the new view controller modally (presentViewController:animated:completion:), or;
(c) add the new view controller to the view controller stack array
manually by assigning a new viewControllers array to the navigation
controller's viewControllers property (setViewControllers:).
I have a view controller which displays a carousel control (iCarousel). The view is rendered correctly and the carousel is displayed. Right after that a modal is displayed which allows the user to agree to certain terms. I want that once they agree I refresh the viewcontroller which contains the carousel control. Basically, I want to rotate the carousel to some random index.
- (IBAction)accept:(id)sender
{
NewsViewController *newsViewController = [self.storyboard instantiateViewControllerWithIdentifier:#"NewsStoryboard"];
[newsViewController loadNews];
[newsViewController.view setNeedsDisplay];
[self dismissViewControllerAnimated:YES completion:nil];
}
The above code does call the loadNews and fetches it but the view is never refreshed.
What happens to the carousel should really be up to the view controller that manages it, not the modal view controller. Make the modal controller do its thing and return whatever data it collects to its parent. The parent (in this case, the carousel's controller) can then look at that data and decide what it needs to do next (refresh, for example).
The problem is this line:
NewsViewController *newsViewController = [self.storyboard instantiateViewControllerWithIdentifier:#"NewsStoryboard"];
That is not the old view controller; it is a new, unused copy of that view controller. You need to create a line of communication from the modal view controller back to the existing view controller.
The typical way to do this is through a delegate, which you set when creating the modal view controller. If you look at the Xcode Utility template, you will see that it illustrates this architecture. The original view controller sets itself as the modal view controller's delegate, and the modal view controller is thus able to talk back to the original view controller as it is dismissed.
This is such an important thing to be able to do that I talk about it at length in my book:
http://www.apeth.com/iOSBook/ch19.html#_presented_view_controller
I have a root view controller (RVC) that opens up a Modal ViewController (MVC). I then navigate within the MVC to few more VC's via a push. What is the best practice to get from one of those VC's back to the RVC?
Normally I have a delegate from the Modal VC that calls up to the RVC which then dismisses the modal, but if you navigate away from it, but I'm not sure how I would do that if you navigate away from it.
Without seeing any code it is a bit hard to help but let me shoot in the dark here.
I will assume that the first controller presented inside the modal view provides the protocol/delegate to call the dismiss action.
If you use UINavigationController inside your modal view to push other view controllers on the stack you can always obtain the first controller like this
UIViewController * yourFirstController = [[[self navigationController] viewControllers] objectAtIndex:0];
// and then use your delegate to call your dismiss method
// you will need to typecast your controller based on your subclass otherwise will get warning here
if ([[yourFirstController delegate] respondsToSelector:#selector(yourCloseProtocolMethod)]) {
[[yourFirstController delegate] yourCloseProtocolMethod];
}
Don't forget that a delegate doesn't have to be a property of a UIViewController inside your model navigation stack. Consider creating a singleton class that holds a reference to the rootviewcontroller as a delegate. That way any class in your application has access to it and you aren't forced to continually pass it through to every UIViewController that requires it.