Get UIViewController to reload different UIView programmatically - objective-c

Question

I am overriding the loadView method within a UIViewController as follows:
-(void)loadView
{
NSLog(#"HPSFormController loadView starting");
HPSFormView* viewForThisController = [ [ HPSFormView alloc ] initWithFrame:_frame ] ;
self.view = viewForThisController;
}
When a certain button is pressed within the view then the same UIViewController gets control again and at this point I wish to completely change the view that the controller is showing. As follows:
-(void)buttonTapped
{
ABCFormView* newview = [ [ ABCFormView alloc ] initWithFrame:_frame ] ;
self.view = newview;
}
However, the buttonTapped method does not load the second view. A completely blank view is shown instead.
How do I get the view controller to reload a completely different view when the button is pressed?

Answer 1

However, the buttonTapped method does not load the second view. A completely blank view is shown instead.
Is it not possible that the problem is in the way you create ABCFormView? I mean, it seems that the original view is replaced by an empty view, so check how the latter is created...
EDIT AFTER YOUR COMMENT:
if you say that the view is "created within a viewDidLoad method within the view controller", then you should instantiate your view controller:
#property (...) ABCFormViewController* newviewController;
....
-(void)buttonTapped
{
self.newviewController = [ [ ABCFormViewController alloc ] init] ;
self.view = newviewController.view;
}
keep in mind that newviewController must be around as long as you are using its controlled view, otherwise you will get a crash. That is the reason why I store its reference in a property.

Answer 2

Obviously you can't get your new view visible by simply setting self.view = newView; because the newView has never been added as a subview to any other views yet - i.e. not in the window.
If you need to switch to a different view, you should probably add APSFormView as a subview to your viewcontroller.view, and when you need to switch, remove APSFormView from superview then add ABCFormView as a new subview to viewcontroller.view.

Answer 3

If your loadView implementation needn't do much else, it may be better to use the storyboard to set it up initially. It is easy to miss, but you can specify in the storyboard that the view should be of a custom type (in the "identity inspector" with the view selected). Further, it may be worth evaluating why a completely different class of view is necessary for the same view controller instance; to me this may be a red flag regarding the application design. You may be better served by a flow between two view controllers, or else write some state-changing logic in this custom UIView-extending class. The decision for me would be made based on the model being represented by the views, along with which behaviors each is designed to facilitate.
If the models are different (i.e. your first view shows a list of accounts, second shows one account detail), or if the behaviors are significantly different (i.e. the first is viewing an account and the second is creating a new one), then I would use two distinct view controllers.
If the models and behaviors are similar, and the style should change, then I would likely write state-changing code in the custom view class to rearrange things, etc.
If you are coming from a different platform, it can seem silly at first, but we really do throw around view controllers without much hesitation. They are elegantly handled by the framework, and are designed to manage "a screenful of content" and be easily swapped for another screenful.

Answer 4

It is hard to tell without knowing what is inside ABCFormViewController. I had some timing issues once on a view controller which I just needed to generate the view because I wanted to capture its content to create a pdf file (its a view that never gets displayed onscreen). In that case I needed to insert a code like this:
[newviewcontroller.view setneedsrefresh];
Before I do
otherVC.view = newviewcontroller.view;
Otherwise I get a blank page.
I believe I get this because by the time everything is sorted out ARC deallocates newviewcontroller so the view is nil. In your case this may not be the problem. Is there a reason why you need a 2nd and 3rd view controller to put into your view because a much simpler way of doing this is to just transfer control to the other view controllers via modal, pop view or a navigationController. Another more usual way is to create multiple views in your XIB and then just load it into a blank view instead of creating view controllers for each of them.