如何将淡化文本交叉到NSTextView，将图像交叉到可可应用程序中的NSImageView？

I have a Cocoa app I'm writing that has an ImageView with a TextView as a subview sitting on top of the ImageView. I have two functions, one that updates the image in the ImageView and one that updates the text in the TextView. Both of those functions work properly, but I would like the new text to fade in or cross fade from the old text. In the same way I would like to cross fade in the new image.I have a Cocoa app I'm writing that has an Imag