Functional Web Development with Elixir, OTP, and Phoenix

Customizing GenServer Behavior

Spawning and initializing a new GenServer process is a great start, but the default callback implementations we got with use GenServer don’t go very far. In order to build real applications, we need to change the way a GenServer behaves to fit each application’s needs.

To do this, we’re going to follow the pattern we’ve used so far—write a client function that wraps a GenServer function that triggers a callback. The callback is where we’ll define the new behavior.

Each time we add a new public function, we build a new piece of the interface for the game. As we go along, we’ll expose more and more of the game’s behavior. This interface acts as a boundary between the rest of the system and a game. That makes it ...