Storyboard, UIViewController and UISplitViewController

seguestoryboarduisplitviewcontrolleruiviewcontroller

Trying to make storyboard based application for iPad. In it I need to transition from start screen (UIViewController) to main screen (UISplitViewController) and then to full-screen view (again UIViewController).

I saw a number of discussions on the web (at least several – on stackoverflow), stating that UISplitViewController can't be used in Storyboard based application any other way than being RootViewController. Some threads contain workarounds and there's also alternative splitview (https://github.com/mattgemmell/MGSplitViewController) to cope with this.

But what I can't understand is why Apple documentation states quite the opposite. Here is the link to the chapter from Apple's iOS 5.0 Library. It states:

Creating a Split View Controller Using a Storyboard

To add a split view controller to your application’s storyboard:

Open your application’s main storyboard.
Drag a split view controller out of the library. This also creates view controllers
for the two panes of the split view controller.
For each of the split view controller’s contained view controllers, use the Identity inspector to set the class name of the view controller.

To present the split view interface, do one of the following:

Display it as the first scene, by selecting the scene and checking
the “Is Initial View Controller” box under the Attributes inspector.
Display it from another scene, by adding a modal segue to to it.
Display it programmatically, by calling the performSegueWithIdentifier:sender: method to initiate a modal segue.

I was trying it in many ways, but approaches described in last two statements never worked.
Both modal segue and performSegue… fail with well-known error:

"*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Application tried to present a Split View Controllers modally…"

Anyone able to explain that? Is this a bug in XCODE/iOS 5.0 or bug in documentation?

Regards,
Petr

Best Answer

According to this Apple article, the split view controller must be the root. Here is a snippet:

A split view controller must always be the root of any interface you create. In other words, you must always install the view from a UISplitViewController object as the root view of your application’s window. The panes of your split-view interface may then contain navigation controllers, tab bar controllers, or any other type of view controller you need to implement your interface. Split view controllers cannot be presented modally.

Related Solutions

IOS – UISplitViewController with storyboard – multiple master views and multiple detail views

If the split view controller delegate was the detail view controller that had been replaced, this is the cause of the crash. The replaced detail view controller is being dealloc'd and so the split view controller delegate is no longer a reference to a valid object.

You can update the delegate in prepareForSegue:sender:. For example:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"MySegue"]) {
        UIViewController *destinationViewController = [segue destinationViewController];
        if ([destinationViewController conformsToProtocol:@protocol(UISplitViewControllerDelegate)]) {
            self.splitViewController.delegate = destinationViewController;
        }
        else {
            self.splitViewController.delegate = nil;
        }
    }
}

Which view controllers you use for delegates is dependent on your view controller hierarchy. In the simplest case, any view controllers that are assigned to splitVC detail will probably need to be delegates. You may want to base them all on a common super class that handles the shared split view controller delegate logic.

Ios – UISplitViewController in portrait on iPhone shows detail VC instead of master

Oh man, this was causing me a headache for a few days and could not figure out how to do this. The worst part was that creating a new Xcode iOS project with the master-detail template worked just fine. Fortunately, in the end, that little fact was how I found the solution.

There are some posts I've found that suggest that the solution is to implement the new primaryViewControllerForCollapsingSplitViewController: method on UISplitViewControllerDelegate. I tried that to no avail. What Apple does in the master-detail template that seems to work is implement the new (take a deep breath to say all of this one) splitViewController:collapseSecondaryViewController:ontoPrimaryViewController: delegate method (again on UISplitViewControllerDelegate). According to the docs, this method:

Asks the delegate to adjust the primary view controller and to incorporate the secondary view controller into the collapsed interface.

Make sure to read up on the discussion part of that method for more specific details.

The way that Apple handles this is:

- (BOOL)splitViewController:(UISplitViewController *)splitViewController
collapseSecondaryViewController:(UIViewController *)secondaryViewController
  ontoPrimaryViewController:(UIViewController *)primaryViewController {

    if ([secondaryViewController isKindOfClass:[UINavigationController class]]
        && [[(UINavigationController *)secondaryViewController topViewController] isKindOfClass:[DetailViewController class]]
        && ([(DetailViewController *)[(UINavigationController *)secondaryViewController topViewController] detailItem] == nil)) {

        // Return YES to indicate that we have handled the collapse by doing nothing; the secondary controller will be discarded.
        return YES;

    } else {

        return NO;

    }
}

This implementation basically does the following:

If secondaryViewController is what we're expecting (a UINavigationController), and it's showing what we're expecting (a DetailViewController -- your view controller), but has no model (detailItem), then "Return YES to indicate that we have handled the collapse by doing nothing; the secondary controller will be discarded."
Otherwise, return "NO to let the split view controller try and incorporate the secondary view controller’s content into the collapsed interface"

The results are the following for the iPhone in portrait (either starting in portrait or rotating to portrait -- or more accurately compact size class):

If your view is correct
- and has a model, show the detail view controller
- but has no model, show the master view controller
If your view is not correct
- show the master view controller

Clear as mud.

Creating a Split View Controller Using a Storyboard

Best Answer

Related Solutions

IOS – UISplitViewController with storyboard – multiple master views and multiple detail views

Ios – UISplitViewController in portrait on iPhone shows detail VC instead of master

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