Functional Web Development with Elixir, OTP and Phoenix/

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Communication Between Players

Communication Between Players

Understand how both players communicate in Islands’ engine.

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Communication between the players

Now, let’s look at how push/3 works inside the GameChannel. Instead of a reply tuple, this will send a new event down the Channel, but only to the original caller. Since we don’t rely on a reply tuple to communicate back to the client, we replace it with {:noreply, socket}.

The path of message passing will look the same as the reply shown in the following figure.

Let’s go to the Channel and change the handle_in/3 clause to use push/3. We could leave the :reply tuple there and get two responses. However, since push/3 will already send a reply, it makes more sense to swap in {:noreply, socket} instead:

Let’s compile the GameChannel so we can see handle_in/3 in action:

def handle_in("hello", payload, socket) do
  push socket, "said_hello", payload 
  {:noreply, socket}
end

New IEx session

Now, let’s head over to Player 1’s console and give it a try:

defmodule IslandsInterface.Application do
  # See https://hexdocs.pm/elixir/Application.html
  # for more information on OTP Applications
  @moduledoc false

  use Application

  def start(_type, _args) do
    children = [
      # Start the Telemetry supervisor
      IslandsInterfaceWeb.Telemetry,
      # Start the PubSub system
      {Phoenix.PubSub, name: IslandsInterface.PubSub},
      # Start the Endpoint (http/https)
      IslandsInterfaceWeb.Endpoint
      # Start a worker by calling: IslandsInterface.Worker.start_link(arg)
      # {IslandsInterface.Worker, arg}
    ]

    # See https://hexdocs.pm/elixir/Supervisor.html
    # for other strategies and supported options
    opts = [strategy: :one_for_one, name: IslandsInterface.Supervisor]
    Supervisor.start_link(children, opts)
  end

  # Tell Phoenix to update the endpoint configuration
  # whenever the application is updated.
  def config_change(changed, _new, removed) do
    IslandsInterfaceWeb.Endpoint.config_change(changed, removed)
    :ok
  end
end
Communicating between players

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