I'm creating my constraints mainly in viewDidLoad. In updateViewConstraints I'm adding or removing some subviews and additionally adding and removing constraints. As a side note I'm using a container with child view controllers and I'm reusing the same view for different orientations (full in landscape, in a popover in portrait).
Because I have my complete setup in updateViewConstraints I have to call it in some situations manually to adapt the visual changes and not to brake the constraints (e.g. when presenting the same view in a popover, or on iOS 7 it is not called on rotation). I also tried to use setNeedsUpdateConstraints and so on but that always broke my constraints.
My question now is am I allowed to call updateViewConstraints manually? Does it has some negative side effects? Or is the flow of my application wrong?
According to Erica Sadun in the excellent iOS Auto Layout Demystified, 2nd Edition, it's perfectly acceptable to call updateViewConstraints directly:
When working with views, you call setNeedsUpdateConstraints (setNeedsUpdate Constraints: on OS X) to indicate that a view needs attention at the next layout pass. With view controllers, you call the updateViewConstraints method directly, generally when setting up (viewWillAppear:) and responding to rotation callbacks.
来源：https://stackoverflow.com/questions/26625706/is-calling-updateviewconstraints-manually-a-good-idea