[Intro to iOS] Project 3: Twitter

[jerrysu]

/cc @thecodepath

[sandofsky]

Overall, very good. This is one of the homeworks with the least I have to critique.

With subscribing for notifications in the app delegate, you're using selector syntax. I've been moving over to NotificationCenter's block syntax; Apple discourages selector based dispatch, for safety. This seems consistent with other places you've been subscribing for notifications, like the composer.

For notification names, I recommend capitalizing them, e.g. "UserDidLogoutNotification", so they're consistent with iOS naming.

You are creating an NSDateFormatter instance with every status. NSDateFormatter is actually pretty expensive to instance, so it's common to cache a static instance and reuse that through the app.