Chapter 25 

  1. What are the downsides of running certain code on the main thread?

a) It can block the UI.

  1. In which circumstances will threading not help your performance?

a) When you have a lengthy layout-related calculation.

  1. Which GCD feature can you use to execute an action when several other actions are done executing?

b) DispatchGroup.

  1. Which of the following is not a benefit of operations?

b) Faster code execution.

  1. What's the maximum number of Operations you can run at the same time?

a) There is no hard limit, iOS decides on the fly.

  1. What is KVO?

a) A way for objects to observe properties of another object.

  1. How do you start executing operations on an operation queue?

c) By adding operations to it.