What mechanisms does iOS provide to support multi-threading?

iOS provides several mechanisms to support multithreading and concurrency in Objective-C applications:

Grand Central Dispatch (GCD)

GCD is a low-level API that simplifies concurrent code execution on multicore hardware. It provides a pool of threads managed by the system and allows you to submit tasks to queues. GCD offers two main types of queues:

• Serial queues execute tasks in the order they are added, one at a time[4][5]
• Concurrent queues execute multiple tasks concurrently[4][5]

NSThread

NSThread allows you to create and manage threads directly. You can create a new thread by initializing an NSThread object and specifying the target object and selector to be executed on the new thread[3].

NSOperation and NSOperationQueue

NSOperation provides an object-oriented way to represent tasks. NSOperationQueue manages a collection of NSOperation objects, executing them concurrently or serially. Operations can have dependencies, allowing you to define execution order[4].

Synchronization Mechanisms

To prevent race conditions and ensure thread safety when sharing data across threads, iOS provides several synchronization mechanisms:

• @synchroni...