添加子视图控制器

1. Call the addChildViewController: method of your container view controller.
   This method tells UIKit that your container view controller is now managing the view of the child view controller.
2. Add the child’s root view to your container’s view hierarchy.
   Always remember to set the size and position of the child’s frame as part of this process.
3. Add any constraints for managing the size and position of the child’s root view.
4. Call the didMoveToParentViewController: method of the child view controller.

Example

- (void)displayContentController:(UIViewController*)content {
    [self addChildViewController:content];
    content.view.frame = [self frameForContentController];
    [self.view addSubview:content.view];
    [content didMoveToParentViewController:self];
}

移除子视图控制器

1. Call the child’s willMoveToParentViewController: method with the value nil.
2. Remove any constraints that you configured with the child’s root view.
3. Remove the child’s root view from your container’s view hierarchy.
4. Call the child’s removeFromParentViewController method to finalize the end of the parent-child relationship.

Example

- (void)hideContentController:(UIViewController *)content {
    [content willMoveToParentViewController:nil];
    [content.view removeFromSuperview];
    [content removeFromParentViewController];
}