Instance Method

updateConstraints

Updates constraints for the view.

Declaration

- (void)updateConstraints;

Discussion

Override this method to optimize changes to your constraints.

To schedule a change, call setNeedsUpdateConstraints on the view. The system then calls your implementation of updateConstraints before the layout occurs. This lets you verify that all necessary constraints for your content are in place at a time when your custom view’s properties are not changing.

Your implementation must be as efficient as possible. Do not deactivate all your constraints, then reactivate the ones you need. Instead, your app must have some way of tracking your constraints, and validating them during each update pass. Only change items that need to be changed. During each update pass, you must ensure that you have the appropriate constraints for the app’s current state.

Do not call setNeedsUpdateConstraints inside your implementation. Calling setNeedsUpdateConstraints schedules another update pass, creating a feedback loop.

See Also

Triggering Auto Layout

- needsUpdateConstraints

A Boolean value that determines whether the view’s constraints need updating.

- setNeedsUpdateConstraints

Controls whether the view’s constraints need updating.

- updateConstraintsIfNeeded

Updates the constraints for the receiving view and its subviews.