Do the data structures used ensure safe operation in parallel streams?

In iOS, standard data structures such as arrays (Array), dictionaries (Dictionary), and sets (Set) are not thread-safe. This means that concurrent access from multiple threads without synchronization can lead to data races and unpredictable behavior.

To ensure safety during parallel operations, the following are used:

• DispatchQueue queues with proper synchronization policies (e.g., serial queue for writing).
• Classes from NSLock, NSRecursiveLock, and other locking mechanisms.
• High-level constructs such as DispatchSemaphore or OperationQueue.

Example of using a serial queue to protect access to an array:

let queue = DispatchQueue(label: "com.example.arrayQueue")
var array: [Int] = []

func appendElement(_ element: Int) {
    queue.sync {
        array.append(element)
    }
}

Thus, safety is achieved not by the data structures themselves but through external synchronization.