How to add subview with flip animation? - ios

Question

If you create a brand new single view app and put this code behind a button:
UIView *blah = [[UIView alloc] initWithFrame:CGRectMake(0,0,100,100)];
blah.backgroundColor = [UIColor grayColor];
[UIView transitionWithView:blah duration:1
options:UIViewAnimationOptionTransitionFlipFromRight
animations:^{
[self.view addSubview:blah];
}
completion:^(BOOL finished){
}];
The subview is added immediately with no animation. If you add the subview first then try to animate it... you get the same problem.
UIView *blah = [[UIView alloc] initWithFrame:CGRectMake(0,0,100,100)];
[self.view addSubview:blah];
[UIView transitionWithView:blah duration:1
options:UIViewAnimationOptionTransitionFlipFromRight
animations:^{
blah.backgroundColor = [UIColor grayColor];
}
completion:^(BOOL finished){
}];
How on Earth do you animate a flip for a subview while or immediately after adding it?

Answer 1

You generally need to have the container that constrains the animation to be in place already:
- (void)viewDidLoad
{
[super viewDidLoad];
CGRect frame = CGRectMake(0, 0, 100, 100);
_container = [[UIView alloc] initWithFrame:frame];
_container.backgroundColor = [UIColor lightGrayColor];
[self.view addSubview:_container];
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
UIView *subview = [[UIView alloc] initWithFrame:_container.bounds];
subview.backgroundColor = [UIColor darkGrayColor];
[UIView transitionWithView:_container
duration:1.0
options:UIViewAnimationOptionTransitionFlipFromRight
animations:^{
[_container addSubview:subview];
}
completion:NULL];
}

Answer 2

This is worth a try:
UIView *blah = [[UIView alloc] initWithFrame:CGRectMake(0,0,100,100)];
blah.backgroundColor = [UIColor grayColor];
[self.view addSubview:blah];
blah.alpha = 0.0; //Or with blah.hidden = TRUE and then FALSE inside the animation block
[UIView transitionWithView:blah
duration:1
options:UIViewAnimationOptionTransitionFlipFromRight
animations:^{
blah.alpha = 1.0;
}
completion:^(BOOL finished){
}];