Returns attributes suitable for creating a dispatch queue with the desired quality-of-service information.
- iOS 8.0+
- macOS 10.10+
- tvOS 9.0+
- watchOS 2.0+
The quality of service you want to give to tasks executed using this queue. Quality-of-service helps determine the priority given to tasks executed by the queue. Specify one of the values
QOS_CLASS_BACKGROUND. Queues that handle user-interactive or user-initiated tasks have a higher priority than tasks meant to run in the background.
A negative offset from the maximum supported scheduler priority for the given quality-of-service class. This value must be less than
0and greater than or equal to
QOS_MIN_RELATIVE_PRIORITY, or else this function returns
An attribute value that may be passed to the
dispatch_queue_create function when creating a dispatch queue.
Call this function prior to calling the
dispatch_queue_create function when you want to create a dispatch queue with a specific quality-of-service level. This function combines the queue type attributes with the quality-of-service information you specify and returns a value that you can pass to the
dispatch_queue_create function. The quality-of-service value you specify using this function takes precedence over the priority level inherited from the dispatch queue’s target queue.
The global queue priorities map to the following quality-of-service classes: