Is it possible to use Sandbox account with iOS app?

Yes I think so. We provide Restful API which support iOS.

We have Swift SDK which should work for iOS: https://github.com/ringcentral/ringcentral-swift

Thanks for replying so quickly Tyler. Yes the REST API is working for me. My question was whether I can sign in to the iOS app with my Sandbox account and test calls/messages, like I can do with the MacOS desktop app. In the MacOS desktop app I have to switch to Sandbox via Cmd+F2 keys; is there anything like that for iOS app to switch to Sandbox environment for sign in?

I thought you were talking about programming.

You want to know how to run the official RingCentral iOS app in sandbox mode, am I right?

Let me see.

Yes, that's correct.