What is the main role and application of DispatchQoS in the system?

DispatchQoS (Quality of Service) in iOS defines the priority and importance of tasks executed in Grand Central Dispatch (GCD) queues. This allows the system to optimally allocate resources, ensuring that more important tasks are completed faster and with higher priority.

Main levels of DispatchQoS:

• userInteractive — for tasks that affect the user interface and require immediate response (e.g., animations).
• userInitiated — for tasks initiated by the user that expect a quick result.
• default — the default level.
• utility — for long-running tasks with low priority, such as data loading.
• background — for background tasks that do not require urgency.

Example of usage:

DispatchQueue.global(qos: .userInitiated).async {
    // Execute a high-priority task
}

Thus, DispatchQoS helps manage task execution priorities, improving app responsiveness and resource utilization.