How to ensure safe concurrent access to resources in a multithreaded environment?

The following approaches are typically used for safe concurrent access to resources in a multithreaded environment on iOS:

• Synchronization using GCD (Grand Central Dispatch) — utilizing serial queues (DispatchQueue) for sequential execution of code, preventing simultaneous access to a resource.

• Using NSLock or other locking mechanisms — for explicit control over access to critical sections.

• Using atomic operations and properties — for example, @synchronized (in Objective-C) or atomic data types.

Example with GCD:

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

func incrementResource() {
    serialQueue.sync {
        sharedResource += 1
    }
}

Here, access to sharedResource occurs sequentially, which prevents data races.

Thus, to ensure safe access, synchronization mechanisms should be used to avoid concurrent modifications of data from different threads.