Actually, we use both methods. You can preprocess the code ahead of time if you want, and serve content that way. We do this for our core frameworks (AppKit a

Actually, we use both methods. You can preprocess the code ahead of time if you want, and serve content that way. We do this for our core frameworks (AppKit and Foundation). Most of our application code is not preprocessed though. One of the benefits of being able to run without having to "compile" (which is essentially what having to preprocess ahead of time is) is that you have a much more dynamic development environment. You can change code, hit refresh, and see your changes immediately reflected, instead of compiling and waiting.