Do classes ensure thread safety?

In iOS, thread safety is not automatically provided by default classes. Many classes in Foundation and UIKit are not thread-safe, so when accessing them concurrently from multiple threads, synchronization must be managed manually.

To ensure safety when working with threads, the following mechanisms are used:

• GCD (Grand Central Dispatch): allows executing tasks on specific queues, avoiding data races.
• NSLock, NSRecursiveLock, @synchronized: locking mechanisms to protect critical sections.
• Atomic operations: for example, using atomic properties in Objective-C, but this does not guarantee complete thread safety.

An example of using GCD for synchronizing access to a shared resource:

let queue = DispatchQueue(label: "com.example.syncQueue")
var sharedResource = 0

func increment() {
    queue.sync {
        sharedResource += 1
    }
}

Thus, the developer must independently ensure thread safety by using appropriate synchronization mechanisms.