How do I animate constraint changes?

Question

I\'m updating an old app with an AdBannerView and when there is no ad, it slides off screen. When there is an ad it slides on the screen. Basic stuff.

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Answer 1

I appreciate the answer provided, but I think it would be nice to take it a bit further.

The basic block animation from the documentation

[containerView layoutIfNeeded]; // Ensures that all pending layout operations have been completed
[UIView animateWithDuration:1.0 animations:^{
     // Make all constraint changes here
     [containerView layoutIfNeeded]; // Forces the layout of the subtree animation block and then captures all of the frame changes
}];

but really this is a very simplistic scenario. What if I want to animate subview constraints via the updateConstraints method?

An animation block that calls the subviews updateConstraints method

[self.view layoutIfNeeded];
[self.subView setNeedsUpdateConstraints];
[self.subView updateConstraintsIfNeeded];
[UIView animateWithDuration:1.0f delay:0.0f options:UIViewAnimationOptionLayoutSubviews animations:^{
    [self.view layoutIfNeeded];
} completion:nil];

The updateConstraints method is overridden in the UIView subclass and must call super at the end of the method.

- (void)updateConstraints
{
    // Update some constraints

    [super updateConstraints];
}

The AutoLayout Guide leaves much to be desired but it is worth reading. I myself am using this as part of a UISwitch that toggles a subview with a pair of UITextFields with a simple and subtle collapse animation (0.2 seconds long). The constraints for the subview are being handled in the UIView subclasses updateConstraints methods as described above.