Swift：将操作添加到 DispatchQueue/OperationQueue 但稍后启动队列

Question

I have data packets coming in but in rare occurrences, the object to handle them isn't ready yet. What I'm doing at the moment is

• adding the data to an array
• have a while (true) loop checking for the objects state
• if the object is ready, pop the array members onto the object

This works but it's pretty ugly. What I was thinking was to add the pending operations to an OperationQueue and then launch the process once the handling object is ready.

However, I cannot find any feature that allows me to have the operations "on hold" until I tell them to start going.

What can I do about that?

Answer 1

you can use NSOperationQueue's isSuspended property.

var isSuspended: Bool { get set }

From Apple's doc:

When the value of this property is false, the queue actively starts operations that are in the queue and ready to execute. Setting this property to true prevents the queue from starting any queued operations, but already executing operations continue to execute. You may continue to add operations to a queue that is suspended but those operations are not scheduled for execution until you change this property to false.

Please note that setting this property to true only prevents the operations which haven't started yet. In your case, you should set this property to true after you initialize a NSOperationQueue object. Once it's ready, set isSuspended to false.