Does anyone know if it is possible to store some custom metadata at the PHAsset level, such
the querying collections can filter based on this data. We kind of want a custom subtype flag.
We know how to store the metadata right in the asset file (e.g. MP4) but it is tough to query
asset collections based on this (or very slow) because each file needs to be opened.
No, I don't think so. What worked reasonably well for us, though, is to use the PHAsset's localIdentifier Property (inherited from PHObject) to look up custom metadata objects that we previously stored in a CoreData-backed dictionary (upon creating the asset). On top of that, we used PHPhotoLibraryChangeObserver to keep the stored metadata in sync with the photo library.
