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Editorial Team
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Asked: 2026-06-13T06:39:45+00:00

I don’t understand when it’s safe to ask about the frame of a UIView

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I don’t understand when it’s safe to ask about the frame of a UIView during the view appearance chain and/or the differences related to that with Storyboard vs a traditional xib.

I created two different, very simple single UIViewController projects in Xcode 4.5.1; in the first I used the standard single view template with a xib and in the second I used Storyboard. The source code for ViewController.m – identical for both projects – is given below. In IB I dragged in a UIScrollView and wired it appropriately to my controller outlet.

As you’ll note in the source, I’m logging out the frame of my scroll view at different points in the view appearance chain. I don’t understand why they are different and/or when I can safely query the UIScrollView frame since it’s (0,0) in viewDidLoad.

ViewController.m

#import "ViewController.h"

@interface ViewController ()
@property (strong, nonatomic) IBOutlet UIScrollView *scrollView;
@end

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    NSLog(@"viewDidLoad scrollView.frame = (%3.0f,%3.0f)",self.scrollView.frame.size.width,self.scrollView.frame.size.height);
}
- (void)viewWillLayoutSubviews {
    NSLog(@"viewWillLayoutSubviews scrollView.frame = (%3.0f,%3.0f)",self.scrollView.frame.size.width,self.scrollView.frame.size.height);    
}
- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    NSLog(@"viewWillAppear scrollView.frame = (%3.0f,%3.0f)",self.scrollView.frame.size.width,self.scrollView.frame.size.height);

}
- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    NSLog(@"viewDidAppear scrollView.frame = (%3.0f,%3.0f)",self.scrollView.frame.size.width,self.scrollView.frame.size.height);
}
@end

Results with xib

2012-10-23 11:49:48.316 ScrollTest[83262:c07] viewDidLoad scrollView.frame = (320,548)
2012-10-23 11:49:48.318 ScrollTest[83262:c07] viewWillAppear scrollView.frame = (320,548)
2012-10-23 11:49:48.321 ScrollTest[83262:c07] viewWillLayoutSubviews scrollView.frame = (320,548)
2012-10-23 11:49:48.328 ScrollTest[83262:c07] viewDidAppear scrollView.frame = (320,460)

Results with Storyboard

2012-10-23 11:49:58.762 ScrollTestStoryboard[83308:c07] viewDidLoad scrollView.frame = (  0,  0)
2012-10-23 11:49:58.763 ScrollTestStoryboard[83308:c07] viewWillAppear scrollView.frame = (  0,  0)
2012-10-23 11:49:58.765 ScrollTestStoryboard[83308:c07] viewWillLayoutSubviews scrollView.frame = (  0,  0)
2012-10-23 11:49:58.772 ScrollTestStoryboard[83308:c07] viewDidAppear scrollView.frame = (320,460)
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1 Answer

  1. Editorial Team

    Answer is viewDidLayoutSubviews. Wish I’d seen about 20 minutes ago. Below is updated source code and log output.

    ViewController.m

    #import "ViewController.h"

@interface ViewController ()
@property (strong, nonatomic) IBOutlet UIScrollView *scrollView;
@end

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    NSLog(@"viewDidLoad scrollView.frame = (%3.0f,%3.0f)",self.scrollView.frame.size.width,self.scrollView.frame.size.height);
}
- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    NSLog(@"viewWillAppear scrollView.frame = (%3.0f,%3.0f)",self.scrollView.frame.size.width,self.scrollView.frame.size.height);

}
- (void)viewWillLayoutSubviews {
    NSLog(@"viewWillLayoutSubviews scrollView.frame = (%3.0f,%3.0f)",self.scrollView.frame.size.width,self.scrollView.frame.size.height);
}
- (void)viewDidLayoutSubviews {
    NSLog(@"viewDidLayoutSubviews scrollView.frame = (%3.0f,%3.0f)",self.scrollView.frame.size.width,self.scrollView.frame.size.height);
}
- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    NSLog(@"viewDidAppear scrollView.frame = (%3.0f,%3.0f)",self.scrollView.frame.size.width,self.scrollView.frame.size.height);
}
@end

    Storyboard output

    2012-10-23 12:12:35.597 ScrollTestStoryboard[87593:c07] viewDidLoad scrollView.frame = (  0,  0)
2012-10-23 12:12:35.599 ScrollTestStoryboard[87593:c07] viewWillAppear scrollView.frame = (  0,  0)
2012-10-23 12:12:35.601 ScrollTestStoryboard[87593:c07] viewWillLayoutSubviews scrollView.frame = (  0,  0)
2012-10-23 12:12:35.602 ScrollTestStoryboard[87593:c07] viewDidLayoutSubviews scrollView.frame = (320,460)
2012-10-23 12:12:35.609 ScrollTestStoryboard[87593:c07] viewDidAppear scrollView.frame = (320,460)
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