IBDesignable drawRect不工作？

我想創建一個IBDesignable，將一個圖標放在按鈕標籤的右側。它在模擬器中工作，但故事板不會將圖標重新定位到右側。IBDesignable drawRect不工作？

@IBDesignable class IconLabelButtonView : UIButton { 

    override init(frame: CGRect) { 
     super.init(frame: frame) 
     self.setup() 
    } 

    required init(coder : NSCoder) { 
     super.init(coder:coder) 
     self.setup() 
    } 

    func setup() { 

    } 


    override func drawRect(rect: CGRect) 
    { 
     super.drawRect(rect) 

     let imageSize:CGSize = self.imageView.frame.size 
     let titleSize:CGSize = self.titleLabel.frame.size 

     let labeledIconButtonBufferMagnitude:CGFloat = 6.0 

     let imagePadding:CGFloat = ceil(labeledIconButtonBufferMagnitude/2) 
     let titlePadding:CGFloat = floor(labeledIconButtonBufferMagnitude/2) 

     self.imageEdgeInsets = UIEdgeInsetsMake(0.0, (titleSize.width + imagePadding), 0.0, -(titleSize.width + imagePadding)) 
     self.titleEdgeInsets = UIEdgeInsetsMake(0.0, -(imageSize.width + titlePadding), 0.0, (imageSize.width + titlePadding)) 

    } 


}

故事板視圖（錯誤）

storyboard view