Add ChildViewController Help Method.

ViewController.m

#pragma mark - help functions
-(void) addChildViewControllerWithIdentifier:(NSString*)identifier inArea:(CGRect)rect closeOtherChildView:(BOOL)isClose toView:(UIView*) toView{
    
    if (isClose) {
        for (UIViewController* vc in self.childViewControllers) {
            [vc.view removeFromSuperview];
            [vc removeFromParentViewController];
        }
    }
    
    UIViewController* controller;
    controller = [self.storyboard instantiateViewControllerWithIdentifier:identifier];
    [self addChildViewController:controller];
    controller.view.frame = rect;
    [toView addSubview:controller.view];
    [controller didMoveToParentViewController:self];
    
}