Hey!
I have a method where I update my collection view's layout parameter and want
to have a completion block invoked when animation completes:
- (void)transitionAnimated:(BOOL)animated
completion:(dispatch_block_t)completion
{
dispatch_block_t updates = ^{
self.layout.maximumScale = self.maximumScale;
};
dispatch_block_t finish = ^{
if (completion) {
completion();
}
};
if (animated) {
self.collectionView.userInteractionEnabled = NO;
[self.collectionView performBatchUpdates:^{
updates();
} completion:^(BOOL finished) {
self.collectionView.userInteractionEnabled = YES;
finish();
}];
}
else {
updates();
[self.layout invalidateLayout];
finish();
}
}
It works as expected if collection view contains some items. But it crashes if
collection view is empty. And it crashes here:
} completion:^(BOOL finished) {
self.collectionView.userInteractionEnabled = YES;
finish(); // ---- CRASH because finish == NULL
}];
Debugger says that finish is nil:
(lldb) p finish
(dispatch_block_t) $1 = <parent is NULL>
What is going on with that block? Any ideas why it gets NULL-ified?
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