ViewController added programmatically looks shifted/transalted (iOS, swift, storyboards) - ios

Question

I'm learning about View Controller Containers and nesting Viev Controllers in iOS, using swift and storyboard.
The problem is - added view is not within the bounds of a parent view.
This is how it looks in interface builder:
The left view is parent view controller, and the white area is view, in which I want to place blue view controller.
I imagine, that the blue view controller should fill this white view.
However, this is how it looks on iPad:
It looks, like the blue view is placed the same amount pixels below the top of white view, as is the white view to the top of the screen.
Here's the code:
class ViewController: UIViewController {
#IBOutlet weak var vcContainer: UIView!
override func viewDidLoad() {
super.viewDidLoad()
var vc = self.storyboard?.instantiateViewControllerWithIdentifier("TestViewController")
displayVC(vc!)
}
func displayVC(content: UIViewController) {
content.view.frame = self.vcContainer.frame
content.view.setNeedsLayout()
self.vcContainer.addSubview(content.view)
self.addChildViewController(content)
content.didMoveToParentViewController(self)
}
}
Any help would be appreciated. Thanks!

Answer 1

This line: self.vcContainer.addSubview(content.view)
it should be self.view.addSubview(content.view)
Because when you set frame for your child viewcontroller like this:
content.view.frame = self.vcContainer.frame
it is relative to parent viewcontroller, not vcContainer, hence after you added content into vcContainer, it's in wrong position.
If you want to add content into vcContainer, you should choose another way to place content.view, something like pin edges of content to edges of vcContainer using NSLayoutConstraint.
Full working code:
UIViewController *vc =
[self.storyboard instantiateViewControllerWithIdentifier:#"vc"];
[self addChildViewController:vc];
vc.view.translatesAutoresizingMaskIntoConstraints = NO;
[self.container addSubview:vc.view];
[self.container addConstraint:[NSLayoutConstraint
constraintWithItem:vc.view
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self.container
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:0]];
[self.container addConstraint:[NSLayoutConstraint
constraintWithItem:vc.view
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:self.container
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:0]];
[self.container
addConstraint:[NSLayoutConstraint
constraintWithItem:vc.view
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:self.container
attribute:NSLayoutAttributeLeading
multiplier:1.0
constant:0]];
[self.container
addConstraint:[NSLayoutConstraint
constraintWithItem:vc.view
attribute:NSLayoutAttributeTrailing
relatedBy:NSLayoutRelationEqual
toItem:self.container
attribute:NSLayoutAttributeTrailing
multiplier:1.0
constant:0]];
[vc didMoveToParentViewController:self];
Adding constraints will be a lot easier if you use PureLayout.

Answer 2

The constraints set in your StoryBoard on your view specify an exact distance to be kept from the top.
This distance is true for some devices, so it might looks like it is in the middle, but on the ipad this is not the case.
You should add a height on your view, and than position vertically and horizontally to the center of your superview.