Type	Topic	Plugin	Version	macOS	Windows	Linux	iOS	Targets
class	Cocoa Threading	MBS MacFrameworks Plugin	8.0	✅ Yes	❌ No	❌ No	❌ No	Desktop, Console & Web

Queues NSOperations for later execution.

Available in Mac OS X v10.5 and later.

The NSOperationQueue class manages a set of NSOperation objects in a priority queue and regulates their execution. Operations remain in the queue until they are explicitly cancelled or finish executing. An application may create multiple operation queues, with each queue running up to its designated maximum number of operations.

A specific NSOperation object can be in only one operation queue at a time. Operations within a single queue coordinate their execution order using both priority levels and inter-operation object dependencies. Operation objects in different queues can coordinate their execution order using dependencies, which are not queue-specific.

Inter-operation dependencies provide an absolute execution order for operations. An operation object is not considered ready to execute until all of its dependent operations have finished executing. For operations that are ready to execute, the operation queue always executes the one with the highest priority relative to the other ready operations. For details on how to set priority levels and dependencies, see NSOperation Class Reference.

You should never manually start an operation while it is sitting in an operation queue. Once added, an operation stays in its queue until it finishes executing or is cancelled.