Answer by Cameron Lowell Palmer for How do I animate constraint changes?

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.