Before I do a lot of fruitless experimenting, does anyone know if you can sort shared albums using the Apple Photokit. I know the native photos app is not able to.
As far i understand from your question, you want to sort based on the timestamp at which asset was added. Try this:
_assets = [[NSArray alloc] init];
PHFetchOptions *options = [[PHFetchOptions alloc] init];
//Sort according to date
options.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:NO]];
//If you want just images
options.predicate = [NSPredicate predicateWithFormat:@"mediaType == %d", PHAssetMediaTypeImage];
//Each album is an assetCollection
PHFetchResult *fetchResult = [PHAsset fetchAssetsInAssetCollection:self.assetsCollection options:options];
_assets = fetchResult;