The iTunes Store was and remains a business in its own right. Its mission isn’t selling music, or movies, or TV shows, or apps, but building an end-to-end system, a platform that allows people to easily buy anything digital. If you think the App Store shouldn’t be “a huge revenue stream” then you’re not seeing things the way Apple does.

Out of all the API calls I saw in grand central dispatch the one that initially impressed me least was dispatch_once. However after reading its documentation and using it a bunch I realized how useful this one API call is. Not only it is a dead simple way to ensure that code only gets executed once, but it is also thread safe.