Asks the delegate to provide the view controller to display in the primary position when the split view interface expands.
- iOS 8.0+
- tvOS 9.0+
The split view controller whose interface is expanding.
The view controller to use as the primary view controller or
nil to specify the current primary view controller.
When the split view controller transitions from a horizontally compact to a horizontally regular size class, it calls this method and asks you for the view controller to display in the primary position when that transition is complete. The view controller you return becomes the primary view controller of the split view interface. If you do not implement this method, or if your implementation returns
nil, the split view controller chooses its current primary view controller as the one to use.
If you specified a specific view controller in your
primary method, use this method to restore the original primary view controller for your split view interface. You can also implement the
split method to disentangle your view controllers from one another as needed.