The Core iOS Developer’s Cookbook, Fifth Edition

Modules for System Frameworks

To use these system sound services, you must include the Audio Toolbox framework and headers. In iOS 7, Apple introduced modules support to Xcode, simplifying the process of adding system frameworks and headers to your code.

In the past, including support for a system framework required adding the framework to your application target and using the #include macro to include the header in your source code. With modules, a sole @import at the top of your source file will include the headers and Auto Link the framework into your project:

@import AudioToolbox;

Modules make it easier to add Apple-provided frameworks to your project. However, their primary purpose is to increase the performance of compilation and code indexing. ...