title: Garbled exception when implementing UIPopoverBackgroundView subclass
body: <p>I've implemented this class as follows:</p>
  
  <pre><code>#import "JKBackgroundView.h"
  
  @implementation JKBackgroundView
  
  static CGFloat jkArrowBase = 26.0;
  static CGFloat jkArrowHeight = 16.0;
  
  // Background image insets
  static CGFloat jkBackgroundTopInset = 68.0f;
  static CGFloat jkBackgroundLeftInset = 16.0f;
  static CGFloat jkBackgroundBottomInset = 16.0f;
  static CGFloat jkBackgroundRightInset = 34.0f;
  
  // Content view insets
  static CGFloat jkContentTopInset = 40.0f;
  static CGFloat jkContentLeftInset = 6.0f;
  static CGFloat jkContentBottomInset = 8.0f;
  static CGFloat jkContentRightInset = 7.0f;
  
  +(CGFloat)arrowBase {
      return jkArrowBase;
  }
  
  -(UIPopoverArrowDirection)arrowDirection {
      return UIPopoverArrowDirectionUp;
  }
  
  -(CGFloat)arrowOffset {
      return 0.0f;
  }
  
  +(CGFloat)arrowHeight {
      return jkArrowHeight;
  }
  
  +(UIEdgeInsets)contentViewInsets {
      return UIEdgeInsetsMake(jkContentTopInset, jkContentLeftInset, jkContentBottomInset, jkContentRightInset);
  }
  
  -(void)drawRect:(CGRect)rect {
      UIEdgeInsets popoverInsets = UIEdgeInsetsMake(jkBackgroundTopInset, jkBackgroundLeftInset, jkBackgroundBottomInset, jkBackgroundRightInset);
      UIImage *popoverImage = [[UIImage imageNamed:@"popover_stretchable.png"] resizableImageWithCapInsets:popoverInsets];
      [popoverImage drawInRect:rect];
  }
  
  -(id)initWithFrame:(CGRect)frame {
      self = [super initWithFrame:frame];
      if (self) {
          self.backgroundColor = [UIColor clearColor];
      }
      return self;
  }
  
  -(void)setArrowDirection:(UIPopoverArrowDirection)arrowDirection {
      // Do nothing
  }
  
  @end
  </code></pre>
  
  <p>I add it to my UIPopoverView (not a subclass) using this code:</p>
  
  <pre><code>_logoutPopover.popoverBackgroundViewClass = [JKBackgroundView class];
  </code></pre>
  
  <p>When I run the project, though, I receive a crazy error message as follows:</p>
  
  <blockquote>
    <p><em>*</em> Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[UIPopoverBackgroundView
    º¯lå] must be implemented by subclassers.'</p>
  </blockquote>
  
  <p>Does anyone has any idea what method it thinks I didn't implement? It appears to just be a bunch of gibberish. Thanks!</p>
  
  <p><strong>Edit</strong> It looks like I forgot to implement setArrowOffset:. It works after adding that. Apple's error message was just garbled.</p>