Hands-On Design Patterns with Swift

Tasks and queues

Queues are objects that abstract series of operations to execute. The system creates many queues for you, but the most important one is probably the main queue. Queues come in two major flavors, as follows:

• Serial: A serial queue guarantees that no two operations will be executed at the same time. This is a particularly interesting feature if you need to write thread-safe code.
• Concurrent: A concurrent queue will let different operations run in parallel, which can also be a very interesting feature.

As we mentioned previously, a serial queue is a queue that guarantees that no two operations will be run in parallel. The main queue of our apps, which you can access through DispatchQueue.main, is a serial queue. This is helpful ...