Animating Constraints

Recipe 5-1 moves a view by removing a constraint that aligns the view to the top or bottom and adding an inverse constraint. The following snippet from Recipe 5-1 moves the view from the top to the bottom:

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NSLayoutConstraint * constraintToMatch =     [NSLayoutConstraint constraintWithItem:view1         attribute:NSLayoutAttributeTop         relatedBy:NSLayoutRelationEqual toItem:self.view         attribute:NSLayoutAttributeTop multiplier:1.0f constant:0]; [self.view removeMatchingConstraint: constraintToMatch]; NSLayoutConstraint * updatedConstraint =     [NSLayoutConstraint constraintWithItem:view1         attribute:NSLayoutAttributeBottom         relatedBy:NSLayoutRelationEqual toItem:self.view ...

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