Using storyboard ,I created a project.
Inside viewDidLoad,I did :
NSLog(@"%@",self.view.description);
I got :
<UIView: 0x8789cb0; frame = (0 20; 320 460); autoresize = RM+BM; layer = <CALayer: 0x8789d50>>
But inside another XXControllerDelegate Method , I got :
<UIView: 0x8789cb0; frame = (0 0; 320 416); autoresize = RM+BM; layer = <CALayer: 0x8789d50>>
I found the fact if I didn’t choose Resize View From NIB 
I always got :
frame = (0 0; 320 416)
But I couldn’t find anywhere resize the view from NIB.Who moved my view ?
Your view has
RM+BMthese anchors will be able to move the view y and x position in regarding to the parent view, whenviewDidLoadis called thesuperviewgets its size from thexibfile, whenviewWillAppearis getting called, the view will resize to thesuperviewIf you want your view to not resize you should remove the
RM+BM, check the screen shotRemove the red horizontal and vertical lines in the right middle part of the image bellow