I have an app that shares files between users of the app by attaching the file to either an email or an iMessage. The original implementation attached a JSON file but I was able to build a smaller binary file, allowing me to have more content within the file size limit. Mail attachments work just fine.
I've modified the info plist to define the app-specific file extension. But no matter where I define it, iMessage refuses to put up a preview where the user can select my app to open it. I tried putting it in a document type with a public.text, public.data roles. I tried adding it to the Exported Type Identifiers as a public-mime-type.
I made sure the identifiers all have the reverse url com.<company>.<appname>.<file extension>
My temporary iMessage workaround is to name the file with .zip, a known public extension. It doesn't have valid zip data, it just declares it as a zip file and allows the user to pick my app to open it because I added zip as an exported type identifier. But I don't want the user to think my app can also open zip files.
I would be happy if the preview looked similar to what is done for zip files - a file icon, but with my app's name inside the icon.
Any help with this configuration nightmare is appreciated. Mike