NSOperationQueue
NSOperationQueue
- Subject: NSOperationQueue
- From: Graham Cox <email@hidden>
- Date: Sat, 02 Jun 2012 13:07:58 +1000
A question about NSOperationQueue:
Is there a way to add operations to the queue so that they "jump the queue" ahead of any operations that are not running and have not been run yet?
Here's my use case:
I have a browser that browses folders full of SVG files. To create a thumbnail preview of the file, it needs to be parsed and converted but it's really slow to do this, so I encapsulate this in an operation and stick it on a concurrent operation queue. The queue limits the number of concurrent ops to a small handful. As each thumbnail is generated, it refreshes the browser and the thumbnail pops into view.
If I'm scrolling through the browser, it may have queued up a large number of these, but ideally I would prefer if it gave priority to those that are actually visible in the window, which are the ones most recently added to the queue. Instead, it adds them to the end which means I often have to wait a long time for the window to show the thumbnails. Setting a higher priority on these items doesn't help because the operations all end up with the same priority.
An NSOperationQueue that simply iterated in reverse would do it, or a way to prepend the objects to the head of the queue.
--Graham
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