This is the main module that you will come in contact with.

you can use this module to inherit its functionality.

What is GenNotify

You can basically think of it as some kind of broadcast/multicast module. It's for forwarding Messages to everyone who is in the list of recipients.

A small Warning

Please be aware that this module can cause a lot of harm if misused. Sending a lot of Notifications to all kinds of recipients can make the your System very messy and it will be very annoying to debug.

TL;DR Do yourself and your colleagues a favor: Don't use this extensively!

Example

defmodule MyNotification do
  use GenNotify

  def on_message(msg) when is_binary(msg) do
    IO.puts("I got a message: #{msg}")
  end

  # we ignore all other kinds of messages
  def on_message(_msg), do: nil
end

somewhere else in the code...

GenNotify.send_notification("im a message") # => This will cause MyNotification.on_message/1 to be called

Example - GenServer

Sometimes a notification for a module isn't quite what you want. You want notifications for a specific Process. GenNotify does support GenServer

defmodule MyGenServer do
  use GenServer
  use GenNotify, gen_server: true # we need to tell GenNotify that this is indeed is a GenServer

  def start_link(_) do
    GenServer.start_link(__MODULE__, :ok)
  end

  def init(_) do
    gen_notify_init() # => This will supply our PID to GenNotify.Notifier (Keep in mind, GenNotify.Supervisor already needs to be alive!)
    {:ok, %{messages: 0}}
  end

  def on_message(msg, state) when is_binary(msg) do
    new_state = %{state | messages: state.messages + 1}
    IO.puts("#{msg} is my #{new_state.messages} message!") # => will be "im a message is my X message!" in our example

    # Give the updated state back to the GenServer
    new_state 
  end

  # we ignore all other kinds of messages
  def on_message(_msg, state), do: state
end

somewhere else in the code...

GenNotify.send_notification("im a message")