Pro Multithreading and Memory Management for iOS and OS X

Chapter 5

Blocks Implementation

In the previous chapters, we learned that a Block is an anonymous function together with automatic variables. In this chapter, we look at the details of a Block with its implementation to see what happens under the hood of Blocks. We start with the basic idea of the Block’s implementation and then we show various situations to see how the Blocks work, such as how automatic variables are captured, how Blocks and __block variables are stored in memory, and how objects are captured by Blocks. Also, we show some pitfalls of Blocks related to circular reference and copy/release methods. All the example source code assumes ARC is enabled except where specified.

Under the Blocks’ Hood

You might think that the Block ...