How do you set stretchableImageWithLeftCapWidth in Interface builder?

Question

How do you set stretchableImageWithLeftCapWidth in Interface builder?

Answer 1

Interface builder does not support stretchable images.

-(void) viewDidLoad {
  [super viewDidLoad];
  [myImageView setImage:[[myImageView image] stretchableImageWithLeftCapWidth:5 topCapHeight:5 ]];
}

Answer 2

This is currently (as of version 4.5) a limitation of InterfaceBuilder. However, having to create an IBOutlet for each button and manually specify that the image is stretchable in viewDidLoad is not a great solution, if for no other reasons than it makes creating the UI more cumbersome and also more brittle.

Instead of that, let's create a UIButton subclass which will always make any background image stretchable by default. In this example I only stretch the normal and highlighted background image. For a production-ready class you would probably want to check all states of both background and foreground images and stretch them.

@implementation NTSTButton

- (id) initWithCoder:(NSCoder *)aDecoder {

    self = [super initWithCoder:aDecoder];
    if (self) {
        /* There is no support in IB for stretchable images. So, let's
           make sure _any_ background image assigned to this button 
           stretches correctly.
           Note: Setting the stretch cap to 10px, which should work with
           almost all button background images. 
        */
        UIImage *normalImage = 
                 [[self backgroundImageForState:UIControlStateNormal]
                        stretchableImageWithLeftCapWidth:10 topCapHeight:10] ;

        UIImage *highlightedImage = 
                 [[self backgroundImageForState:UIControlStateHighlighted]
                        stretchableImageWithLeftCapWidth:10 topCapHeight:10] ;

        [self setBackgroundImage:normalImage 
              forState:UIControlStateNormal];

        [self setBackgroundImage:highlightedImage 
              forState:UIControlStateHighlighted];
    }
    return self;
}

@end