Mis juhtub, kui käivitate järjestikuses järjekorras asünkroonse ülesande?

The task will be executed, but not immediately. It will be placed in a queue and executed sequentially with other tasks in this queue, as they are completed. Despite the task being asynchronous, its execution will be limited by the nature of a single-threaded serial queue.

// Example
let serialQueue = DispatchQueue(label: "com.example.serialqueue")

serialQueue.async {
    // This task executes asynchronously,
    // but will wait for the completion of previous tasks in the queue
    print("Task 1 completed")
}

serialQueue.async {
    // This task executes asynchronously,
    // but will wait for task 1 to complete
    print("Task 2 completed")
}

Key points:

• Sequence: Tasks are executed in the order they were added.
• One thread: At any given moment, only one task from this queue is executing.
• Does not block the caller thread: The call to async does not block the thread that calls it. The task is enqueued and control is returned.
• Asynchronous within the task: If the task contains asynchronous operations (e.g., a network request), these internal operations can run on other threads, but the task in the serial queue will not proceed to the next until the current task is finished (from the queue's perspective).