Thats totally possible, so in the user_socket.ex file you add a room as "room:name:*". Just add whatever you want after the star when joining the channel and boom your off.

For example I have a team channel defined like :

channel("team:*", TpPhoenixWeb.RequestCounterChannel)

The user then joins a channel named "team:API_KEY_HERE" and only they can see what is broadcast there.

To be clear, what the macros in user_socket do is route topics that have a particular prefix to a particular channel module. You could make a generic one:

channel "generic:*", GenericChannel

Then you can put literally anything after generic:

I believe that you can meaningfully accomplish this task without creating a macro as specified by @benwilson512 above. And in general if you can accomplish something with just modules and functions then use that approach. Quoth the Elixir docs: “Macros should only be used as a last resort”.