// Configure an alternative FIRApp.
FirebaseApp.configure(name: "secondary", options: secondaryOptions)

// Retrieve a previous created named app.
guard let secondary = FirebaseApp.app(name: "APPNAME")
  else { assert(false, "Could not retrieve APPNAME app") }

// Retrieve a Real Time Database client configured against a specific app.
let secondaryDb = Database.database(app: secondary)