Quick Chat for iOS is a Swift source code example showing how to create a real-time chat app using Google’s Firebase form Haik Aslanyan.
Firebase is great for these types of apps because of its real-time database, and generous free tiers. Quick Chat features logins, real-time text messages, photos, and locations.
This animation from the readme shows Quick Chat in action:
You can find Quick Chat on Github here.
A nice example of an iOS chat app using Firebase.