What approaches to task processing in multithreading do you know?

In iOS, the following approaches are often used for handling tasks in multithreaded mode:

1. GCD (Grand Central Dispatch) — a low-level API for managing task queues. It allows creating serial and concurrent queues, executing tasks asynchronously or synchronously.

DispatchQueue.global(qos: .background).async {
    // Background task
    DispatchQueue.main.async {
        // UI update
    }
}

2. Operation and OperationQueue — a higher-level mechanism that allows creating operations with dependencies, cancellation, and priorities.

let operationQueue = OperationQueue()
let operation = BlockOperation {
    print("Executing task")
}
operationQueue.addOperation(operation)

3. NSThread — a lower-level way of creating and managing threads, used less frequently due to complexity.

4. Swift Concurrency (async/await) — a modern approach for asynchronous programming that simplifies working with multithreading.

Task {
    await fetchData()
}

The choice of approach depends on the task, the required level of control, and code maintainability.