Add/Remove ChildViewController

childViewController

//add:
UIViewController *childVC = ...;
[childVC willMoveToParentViewController:self];
[self addChildViewController:childVC];
[self.view addSubview:childVC.view];
//set frame or constraints of childVC.view
[childVC didMoveToParentViewController:self];


//remove:
[childVC willMoveToParentViewController:nil];
[childVC.view removeFromSuperview];
[childVC removeFromParentViewController];