Original images being fetched again on app update

[derek-maurer]

I noticed something in my app when I update it on the App Store. The images in the collection view flash briefly because fast image cache is, for some reason, getting them from the original files on disk again instead of getting them from the cache. (logical conclusion because it does the exact same thing UI wise if you delete the cache files)

When the app gets updated the files in the ImageTables directory seem to be there and the same size before and after the app gets updated. However, I can't seem to figure out why FastImageCache would be getting the original image files when the image tables seem to still exist. This is hard to debug because it only seems to occur when the app updates. I was hoping someone else had run into this issue and could give me some guidance.

Thanks!

[derek-maurer]

I figured out the issue. I copied and pasted most of the demo app code into my app to get Fast Image Cache up and running. However, it looks like there's a flaw in the demo app. The UUID method in the model class sets an MD5 hash of the full image file path. If you take a look at that path, Apple sets a random string for the folder name of your app (a hash of the app name maybe?). That random string can change when the app gets updated. Since the folder name gets changed the hash of the full image path will no longer be equal to the hash of the image path before the update.

The UUID method should hash the lastPathComponent of the sourceImageURL to prevent this issue.

NSString *imageName = [_sourceImageURL lastPathComponent];
CFUUIDBytes UUIDBytes = FICUUIDBytesFromMD5HashOfString(imageName);
_UUID = FICStringWithUUIDBytes(UUIDBytes);

[mallorypaine]

Thanks for the tip. I updated the demo app.