How can race conditions be prevented in a multithreaded environment?

To prevent race conditions in a multithreaded environment on iOS, synchronization mechanisms are used to ensure sequential access to shared resources:

• Semaphores and mutexes (e.g., DispatchSemaphore, NSLock) — block access to critical sections of code until another thread releases the resource.
• Serial Dispatch Queues — serial GCD queues that guarantee tasks are executed one after another.
• Atomic operations — operations that are executed entirely without interruption.
• Using @synchronized — syntactic sugar for locking objects.

Example using DispatchQueue:

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

serialQueue.async {
    sharedResource += 1
}

serialQueue.async {
    sharedResource += 1
}

Here, changes to sharedResource happen sequentially, which prevents race conditions.