Having issue updating hud ivar during in-app purchase - ios5

Question

I have recently set-up an in-app purchase mechanism in my app. During the purchase i would like to update an hud (i am using the mbprogresshud) according to two kinds of events: i start a purchase and i receive a validation of the purchase. The problem i am facing is that the hud is never updated with the one i want when the purchase is done (custom view):
When i click on the purchase button:
-(IBAction)buyButtonTapped:(id)sender {
self.hud = [[SCLProgressHUD alloc] initWithView:self.view];
[self.view addSubview:self.hud];
self.hud.labelText = #"Connecting...";
self.hud.minSize = CGSizeMake(100 , 100);
[self.hud show:YES];
...
}
When i receive a notification that the purchase was successful:
-(void)productPurchased:(NSNotification *)notification {
self.hud.customView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"checkmark_icon.png"]];
self.hud.mode = SCLProgressHUDModeCustomView;
self.hud.labelText = #"Thanks for your purchase!";
...
}
Setting the self.hud.customView property in the last method will trigger a [self setNeedsLayout]; and [self setNeedsDisplay] within the hud class but still i don't observe any change.
Any possible idea of what i am doing wrong here?

Answer 1

As mentioned on the mbprogress hud readme, update of the UI when tasks are performed on the main thread required a slight delay to take effect. What happen in my case is that the hud was a strong property of a popover controller that i dismiss immediately so i didn't get a chance to see the update happening. I now dismiss the controller in the completion block of:
-(void)showAnimated:(BOOL)animated
whileExecutingBlock:(dispatch_block_t)block completionBlock:(void
(^)())completion
And my code snippet look like like this for the dismiss:
[_hud showAnimated:YES whileExecutingBlock:^(void){
[self.successPurchaseSoundEffect play];
_hud.customView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"checkmark_icon.png"]];
_hud.mode = SCLProgressHUDModeCustomView;
_hud.labelText = #"Thanks!";
// We need to pause the background thread to let the music play and the hud be updated
sleep(1);}
completionBlock:^(void){
[self.delegate dismissPurchaseInfoController:self];
}];