iOS Components and Frameworks: Understanding the Advanced Features of the iOS SDK

Introduction to Queues

Some of the terminology related to concurrent processing can be a bit confusing. A “thread” is a commonly used term; in the context of an iOS app, a thread is a standard POSIX thread. Technically, a thread is just a set of instructions that can be handled independently within a process (an app is a process), and multiple threads can exist within a process, sharing memory and resources. Since threads function independently, work can be split across threads to get it done more quickly. It is also possible to run into problems when multiple threads need access to the same resource or data. All iOS apps have a main thread that handles the run loop and updating the UI. For an app to remain responsive to user interaction, the ...