Frame size relative to device and orientation - objective-c

Question

I have created a paginated UIScrollView with three subviews. It works great when testing on an iPhone 5 in landscape (the orientation I designed at) but it breaks whenever the device resolution changes.
How can I make the frame scale to the correct resolution, no matter the device or orientation?
- (void)viewDidLoad {
CGRect frame;
frame.origin.x = self.scrollView.frame.size.width * i;
frame.origin.y = 0;
frame.size = self.scrollView.frame.size;
}
- (IBAction)changePage {
CGRect frame;
frame.origin.x = self.scrollView.frame.size.width * self.pageControl.currentPage;
frame.origin.y = 0;
frame.size = self.scrollView.frame.size;
[self.scrollView scrollRectToVisible:frame animated:YES];
pageControlBeingUsed = YES;
}

Answer 1

Put your scroll view inside another, custom view. In the custom view, implement layoutSubviews something like this.
#interface ViewScalesOneSubview : UIView
#property UIView *scalingSubview;//subview to scale
#end
#implementation ViewScalesOneSubview
-(void) layoutSubviews {
[super layoutSubviews];
CGRect parentBounds = [self bounds];
CGRect childBounds = [scalingSubview bounds];//unscaled
CGFloat scale = parentBounds.width / childBounds.width;
CGAffineTransform transform = CGAffineTransformMakeScale( scale , scale );
//fiddle with x,y translation to position as you like
scalingSubview.transform = transform;
}
#end
Give the custom view autoresizing so it fits the window or whatever container and changes with rotation. Do not give the scroll view autoresizing, as it will conflict with this custom layoutSubviews. When the custom view changes size, it will scale the scalingSubview to fit. By using the same scale for both axis, it will preserve aspect ratio. You could scale to fit instead, or use height instead of width or whatever.
Edit:
To resize the view, as opposed to scaling the view, set the autoresizing mask.
scrollView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
https://developer.apple.com/library/ios/documentation/uikit/reference/UIView_Class/UIView/UIView.html#//apple_ref/occ/instp/UIView/autoresizingMask
You can also do this in interface builder.