Sharing UIImageView between View Controllers in TabBar - iphone

Question

I have a UITabBarController based app. I've made a masterVC Class, all ViewControllers that make up the tabBarController are subclasses of the masterVC. I want to set an UIImageView (which is a property of masterVC) that once set shows that image on each view within the tabBarController.
If I was instantiating each VC I could pass the image as a property (this would be simple). However, there's no method to do this between tabBarController ViewControllers.
The easiest conceptual example of what I'm trying to do is by this example in each view Controller within the tabBarController. There has to be a better way:
-(void)viewDidAppear:(BOOL)animated
{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSData *data = [defaults objectForKey:kMainImageData];
if (data) {
self.mainImageView.image = [NSKeyedUnarchiver unarchiveObjectWithData:data];
}
}
-(void)viewWillDisappear:(BOOL)animated
{
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:self.mainImageView.image];
[[NSUserDefaults standardUserDefaults] setObject:data forKey:kMainImageData];
}

Answer 1

Well there is, create a proper data source, where each UIViewController can request data. There are some ways:
Save the image to disk, use a helper class to retrieve it.
Save the image as property of a Singleton and retrieve it.

Answer 2

You could overload the method
-(id) initWithCoder:(NSCoder*)aDecoder
With something like this:
self = [super initWithCoder:aDecoder];
if ( self )
{
static UIImage *reuseImage = nil;
if ( reuseImage == nil )
{
//Init reuseImage with your image
}
myImageViewProperty.image = reuseImage;
...
return self;

Answer 3

If I'm understanding you correctly, I think you can do this all in your superclass with key-value observing.
In your masterVC header, declare:
#property (strong) UIImage *sharedImage;
And in the implementation:
#synthesize sharedImage;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
[self addObserver:self forKeyPath:#"sharedImage" options:NSKeyValueObservingOptionNew context:NULL];
}
return self;
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
if ([keyPath isEqualToString:#"sharedImage"]) {
self.mainImageView.image = self.sharedImage;
}
}
- (void)dealloc {
[self removeObserver:self forKeyPath:#"sharedImage"];
}
Then, whenever the sharedImage property is set on any of the subclasses, your image view will update its contents accordingly.

Answer 4

I think the easiest thing would be to move the viewDidAppear method you posted into your masterVC class. Then in your ViewControllers that subclass masterVC you can:
Remove the viewDidAppear method if you have no other setup to do, it will then call the viewDidAppear that is in your masterVC.
OR
Change viewDidAppear to the following so that it will call viewDidAppear in masterVC then do all your other setup.
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
// your other code...
}