Objective-C/Swift (iOS) When are the auto-constraints applied in the View/ViewController work flow?

I'm having some issues of figuring out when the auto-contraints setup on a XIB are applied in the view setup process.

For more explanation:

• I've setup a XIB for a view
• I set the "Simulated Metrics" Size to iPhone 3.5-Inch
• I've added auto-constraints to the subviews inside this view
• In the View Controller I perform certain operations dependent on the subview (IBOutlet) frames/bounds in the viewDidLoad method
• In the View I perform certain operations dependent on the subview (IBOutlet) frames/bounds in the awakeFromNib method

In those 2 methods (ViewController::viewDidLoad and View::awakeFromNib) the IBOutlet views HAVE been loaded but the constraints have no yet been applied. The actual frame is still set to the iPhone 3.5" size (width 320) when using a larger simulator (such as the iPhone 6 simulator).

When are these auto-constraints applied and when should any necessary operations that would need the ACTUAL frame/bounds of the subviews take place?

I'm using XCode 6.3, Swift (1.2)

The constraints are applied in the layoutSubviews method. So if you want to do something after they are applied in a UIView subclass, override the method:

   override func layoutSubviews() {
    super.layoutSubviews()
    //the frames have now their final values, after applying constraints
  }

In a UIViewController subclass, use viewDidLayoutSubviews for the same purpose:

  override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    //the frames have now their final values, after applying constraints
  }

Please note that you shouldn't set frame / bounds for a view if you added auto layout constraints to this view.