Question

I know normally I have two choices of places: Temporary folder or Cache folder.

But can anyone tell me the exact differences?

My app will download quite many images upon users’ requests. Of course, no one need them on the disk of iphone permanently. But I still need to cache them in the case users will go back to see them in relatively short time period.

Temporary folder can be one place to go, as I understand it will be cleared by the system. But when will it be cleared?

For cache folder, will cache folder be cleared regularly as well? If the cache folder will not be cleared, and I write the images to Cache folder, that will occupy too much spaces in a longer term, and it is not good for the users of course.

So, can someone give me some hints and tell me the exact diff between these two folders?

Thanks

Answer 1

I would go with the Caches folder— look in NSPathUtilities.h for the relevant methods to get at that one. The Caches folder won’t be backed up, but it won’t necessarily be emptied either, and neither will the temp folder. /tmp would normally be cleared upon reboot (well, potentially), but on the iPhone that’s not something that will happen commonly.

The best approach would be to put data into the Caches folder using some date-based scheme, so that you can clear its contents yourself when you deem it useful to do so. You could use the file’s creation or modification date to inform this decision, and simply scan at each launch (or each enter-foreground event) to determine which items are old enough that they should be removed.