It’s easy to forget which order to send the messages when adding a child view controller for containment in another parent view controller. Here’s a straight to the point look-up when you need it.

Adding a child view controller

parent.addChildViewController(child)
parent.view.addSubview(child.view)
child.didMoveToParentViewController(parent)

Removing a child view controller

child.willMoveToParentViewController(nil)
child.view.removeFromSuperview()
child.removeFromParentViewController()

Extending UIViewController for convenience

With this extension, adding a child is simplified to parent.addContainedChildViewController(child). Then when removing the child, all that needs to be done is child.breakContainment().

extension UIViewController {
/**
Convenience function to add a child view controller to self.
This will send the proper notifications to the child view controller
and add the child view controller's view to `self.view`.
- parameter child: The view controller that should be contained in `self`.
*/
func addContainedChildViewController(child: UIViewController) {
addContainedChildViewController(child, inView: view)
}
/**
Convenience function to add a child view controller to self.
This will send the proper notifications to the child view controller
and add the child view controller's view to the provided `parentView`.
- parameter child: The view controller that should be contained in `self`.
- parameter parentView: The view in which to add the child's view.
*/
func addContainedChildViewController(child: UIViewController, inView parentView: UIView) {
addChildViewController(child)
parentView.addSubview(child.view)
child.didMoveToParentViewController(self)
}
/**
Convenience function to break containment with a parent view controller.
Calling this on a child/contained view controller will call the
proper methods to have it removed. It will send the proper notifications
to the child view controller.
*/
func breakContainment() {
willMoveToParentViewController(nil)
view.removeFromSuperview()
removeFromParentViewController()
}
}
view raw ViewControllerContainment.swift hosted with ❤ by GitHub