Adds a constraint on the layout of the receiving view or its subviews.
- iOS 6.0+
- tvOS 9.0+
The constraint to be added to the view. The constraint may only reference the view itself or its subviews.
The constraint must involve only views that are within scope of the receiving view. Specifically, any views involved must be either the receiving view itself, or a subview of the receiving view. Constraints that are added to a view are said to be held by that view. The coordinate system used when evaluating the constraint is the coordinate system of the view that holds the constraint.
When developing for iOS 8.0 or later, set the constraint’s
active property to
YES instead of calling the
add method directly. The
active property automatically adds and removes the constraint from the correct view.