I'm studying swift by following stanford's lecture on iOS development. I'm currently adding an imageView to the storyboard. I have added an image to the imageView. However, I'm not sure what I have done, but suddenly the image turned into this:
I'm NOT asking for specific solution to the problem. I just want to know in general, what are some of the reasons that the image added could turn into a question mark. Thanks in advance for any help!