Setting up

In this technique project we're going to return to project 7 to solve a critical problem using one of the most important Apple frameworks available: Grand Central Dispatch, or GCD. I already mentioned the problem to you, but here's a recap from project 7:

By downloading data from the internet in viewDidLoad() our app will lock up until all the data has been transferred. There are solutions to this, but to avoid complexity they won't be covered until project 9.

We're going to solve this problem by using GCD, which will allow us to fetch the data without locking up the user interface. But be warned: even though GCD might seem easy at first, it opens up a new raft of problems, so be careful!

If you want to keep your previous work for reference, take a copy of project 7 now and call it project 9. Otherwise, just modify it in place.