Last In-First Out Stack with GCD?

Question

I have a UITableView that displays images associated with contacts in each row. In some cases these images are read on first display from the address book contact image, and

Answer 1

I haven't tried this - just throwing ideas out there.

You could maintain your own stack. Add to the stack and queue to GCD on the foreground thread. The block of code you queue to GCD simply pulls the next block off your stack (the stack itself would need internal synchronization for push & pop) and runs it.

Another option may be to simply skip the work if there's more than n items in the queue. That would mean that if you quickly got the queue backed up, it would quickly press through the queue and only process < n. If you scroll back up, the cell reuse queue, would get another cell and then you would queue it again to load the image. That would always prioritize the n most recently queued. The thing I'm not sure about is how the queued block would know about the number of items in the queue. Perhaps there's a GCD way to get at that? If not, you could have a threadsafe counter to increment/decrement. Increment when queueing, decrement on processing. If you do that, I would increment and decrement as the first line of code on both sides.

Hope that sparked some ideas ... I may play it around with it later in code.