Questions regarding the diskStorage cache

[FaizanDurrani]

Hello,

I am trying to implement a semi-persistent cache for Kingfisher.

I've observed that the default disk cache url points to the .cachesDirectory which the OS can clear based on storage pressure.

My question is, what are the consequences of changing the disk cache url to point to .documentDirectory such that iOS doesn't clear it based on the storage remaining?

I am aware that this significantly increases the size of the document directory but apart from that, is there any restrictions on Kingfisher's end?

I have testers reporting that their image cache is being cleared between app restarts even when the url points to the document folder, is there something that I should be doing along with setting directory in Config initialiser? apparently I had legacy code that was interfering with the sizeLimit causing the cache to clear due to exceeding size limit. The other questions still apply though.

[onevcat]

There should be no restriction from Kingfisher to write the cached images to the .documentDirectory. However, it apparently violates Apple's guideline of "putting the re-generatable contents to cache folder". I am not sure if Apple would reject this in the review or not, so use it at your risk.

Besides of the sizeLimit, there is also an expiration duration inside Kingfisher to clear outdated cached images from time to time. Refer to the wiki for more. Basically, you may want to also set it:

cache.diskStorage.config.expiration = .never

[FaizanDurrani]

However, it apparently violates Apple's guideline of "putting the re-generatable contents to cache folder". I am not sure if Apple would reject this in the review or not, so use it at your risk.

Hmm, I am using Kingfisher diskStorage as an offline store for the thumbnails for items in the database, such that if you open up the app without an active internet connection there's a good chance that the images are still available without relying on iOS to not clear the cache.

I believe this is a good enough reason to switch from the temporary cache folder (as it's no different from just downloading the thumbnails for items in the db).