Container Views

Question

I am trying to get my head around child view controllers. I make a simple project with a main view controller.

Step 1: In that view controller I put a UIButton that is supposed to make a child view appear.

Step 2: I add a container view and put a red background for visibility and a button that will later dismiss it.

I run the project to see what it looks like so far.

Now, the first problem that I encounter is that I don't want the child view to be visible from the begining, I want it to appear when I hit the green button. So I know I'll have to hide it somehow. The two options I have looked at so far are

self.vc.view.hidden = YES;

self.vc.view.alpha = 0;

But the question that I have is that I don't fully understand how to access this child view controller to do either. Am I right to think something along these lines:

h file for the parent view controller:

#import <UIKit/UIKit.h>
#import "ChildViewController.h"

@interface ViewController : UIViewController

@property ChildViewController *vc;

- (IBAction)CreateChildVC:(id)sender;

@end

m file:

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.vc = [[ChildViewController alloc]init];
    [self addChildViewController:self.vc];
    [self.view addSubview:self.vc.view];
    self.vc.view.hidden = YES;
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)GoToView2:(id)sender {

}

@end

This is not working as when I run it the child view is visible. I have tried changing something drastic like the color background to black via:

self.vc.view.backgroundColor = [UIColor blackColor];

and it's not affecting the child view controller in any way. Do I have to use something like

   self.vc = [self.storyboard instantiateViewControllerWithIdentifier:@"ChildVC"];

There are so many options it's easy to get lost. Any help much appreciated.