My iOS client is built with a C++ GUI library, but the result is not that good. So going iOS native. The only reason to use Swift is that I can use my C++ backend code and #nostr API . So using Swift just for the UI part 
GitHub
GitHub - pedro-vicente/nostr_client_relay: Nostr client and relay is a C++ engine that allows to build Nostr applications for command line, desktop or web.
Nostr client and relay is a C++ engine that allows to build Nostr applications for command line, desktop or web. - pedro-vicente/nostr_client_relay