GenServer.handle_cast

You're seeing just the callback handle_cast, go back to GenServer module for more information.
Link to this callback

handle_cast(request, state)

View Source (optional)

Specs

handle_cast(request :: term(), state :: term()) ::
  {:noreply, new_state}
  | {:noreply, new_state, timeout() | :hibernate | {:continue, term()}}
  | {:stop, reason :: term(), new_state}
when new_state: term()

Invoked to handle asynchronous cast/2 messages.

request is the request message sent by a cast/2 and state is the current state of the GenServer.

Returning {:noreply, new_state} continues the loop with new state new_state.

Returning {:noreply, new_state, timeout} is similar to {:noreply, new_state} except that it also sets a timeout. See the "Timeouts" section in the module documentation for more information.

Returning {:noreply, new_state, :hibernate} is similar to {:noreply, new_state} except the process is hibernated before continuing the loop. See handle_call/3 for more information.

Returning {:noreply, new_state, {:continue, continue}} is similar to {:noreply, new_state} except handle_continue/2 will be invoked immediately after with the value continue as first argument.

Returning {:stop, reason, new_state} stops the loop and terminate/2 is called with the reason reason and state new_state. The process exits with reason reason.

This callback is optional. If one is not implemented, the server will fail if a cast is performed against it.