Rename "ballView" to "BallView" and add "-" before BallView instance methods.

I'm not sure exactly why, but Xcode has trouble figuring out the difference between your "ballView" class and properties named "ballView." Hence, you should follow the convention of always capitalizing the class name (in this case "BallView").

You also left out the "-" character before each of the instance methods in the BallView class.

I also moved the BallView.m and .h files into the ballsy directory, where they belong.

Merge this pull request to try out my fix. I was able to run your app in the simulator.