An NSLayoutConstraint has one or two views that it constrains. In your case, the views are self.logoImageView and self.view.

To have any effect, the constraint must be installed on a view, and not just any view. The constraint must be installed on a common ancestor of both constrained views. (Note that a view is considered to be an ancestor of itself.) And when you remove a constraint, you must remove it from the view on which it is installed.

You're trying to remove the centering constraint from self.logoImageView, but the constraint can't have been installed on that view. Instead, the constraint is probably installed on self.view. So try this instead:

[self.view removeConstraint:self.logoImageViewYCenterConstraint]; 

Note also that if you want to animate the image view back to the center, you'll need to uninstall topSpaceConstraint and reinstall self.logoImageViewYCenterConstraint.

A different way to handle this is to install both constraints simultaneously, but give one of them a lower priority. When you need to change the position of the image view, change the priorities of the constraints. Thus:

- (void)viewDidLoad { [super viewDidLoad]; if (self.topSpaceConstraint == nil) { self.topSpaceConstraint = [NSLayoutConstraint constraintWithItem:...]; self.topSpaceConstraint.priority = 1; [self.view addConstraint:self.topSpaceConstraint]; } } - (void)setImageViewCenteredVertically:(BOOL)isCentered animated:(BOOL)animated { if (isCentered) { self.topSpaceConstraint.priority = 1; self.logoImageViewYCenterConstraint.priority = UILayoutPriorityRequired; } else { self.topSpaceConstraint.priority = UILayoutPriorityRequired; self.logoImageViewYCenterConstraint.priority = 1; } if (animated) { [UIView animateWithDuration:1 delay:0 options:UIViewAnimationOptionCurveEaseInOut | UIViewAnimationOptionAllowUserInteraction animations:^{ [self.view layoutIfNeeded]; } completion:nil]; } } 

An NSLayoutConstraint has one or two views that it constrains. In your case, the views are self.logoImageView and self.view.

To have any effect, the constraint must be installed on a view, and not just any view. The constraint must be installed on a common ancestor of both constrained views. (Note that a view is considered to be an ancestor of itself.) And when you remove a constraint, you must remove it from the view on which it is installed.

You're trying to remove the centering constraint from self.logoImageView, but the constraint can't have been installed on that view.

As of iOS 8.0, the preferred (and easiest) way to uninstall a constraint is to set its active property to NO:

self.logoImageViewYCenterConstraint.active = NO; 

Prior to iOS 8.0, you have to remove it from the view where it's installed. The constraint is probably installed on self.view. So try this instead:

[self.view removeConstraint:self.logoImageViewYCenterConstraint]; 

Note also that if you want to animate the image view back to the center, you'll need to uninstall topSpaceConstraint and reinstall self.logoImageViewYCenterConstraint.

A different way to handle this is to install both constraints simultaneously, but give one of them a lower priority. When you need to change the position of the image view, change the priorities of the constraints. Thus:

- (void)viewDidLoad { [super viewDidLoad]; if (self.topSpaceConstraint == nil) { self.topSpaceConstraint = [NSLayoutConstraint constraintWithItem:...]; self.topSpaceConstraint.priority = 1; [self.view addConstraint:self.topSpaceConstraint]; } } - (void)setImageViewCenteredVertically:(BOOL)isCentered animated:(BOOL)animated { if (isCentered) { self.topSpaceConstraint.priority = 1; self.logoImageViewYCenterConstraint.priority = UILayoutPriorityRequired; } else { self.topSpaceConstraint.priority = UILayoutPriorityRequired; self.logoImageViewYCenterConstraint.priority = 1; } if (animated) { [UIView animateWithDuration:1 delay:0 options:UIViewAnimationOptionCurveEaseInOut | UIViewAnimationOptionAllowUserInteraction animations:^{ [self.view layoutIfNeeded]; } completion:nil]; } }