GenFRP

GenFRP is a library that allows for programming in elixir using the Functional Reactive Programming method.

This is a way to store and dispatch information that is very readable and extensible.

The idea is as follows:

1. Your FRP module contains use GenFRP, initial_state: some_useful_starting_state. (some_useful_starting_state can be anything you wish, of course)
2. It implements the update(state, event) :: state function.
3. It implements the render(state, last_rendered_state) :: any function.

update is called whenever an event is sent to the GenFRP process by using GenFRP.send_event(frp_pid, whatever_you_want_to_send).

render is called whenever you want to know its current state (in some representation format that is useful for the outside world, i.e. rendered). GenFRP uses a very simple caching mechanism to ensure that render is only invoked when the internal state has changed since its last invocation.

Here is a very simple example (which can be found as GenFRP.Example.Map as well)

defmodule GenFRP.Example.Map do
  use GenFRP

  def init, do: %{}

  def update(state, [{key, val}]) do
    Map.put(state, key, val)
  end

  def update(state, event) do
    IO.puts "Unrecognized event passed to `#{inspect(__MODULE__)}.update/2`: #{event}"
  end
  
  @doc """
  Returns the key-value pairs as strings, separated over multiple lines, in alphabetical order.
  """
  def render(state, last_rendered_state) do
  Enum.map(state, fn {key, val} ->
      "`#{key}`: `#{val}`"
    end)
  end
  Enum.join("\n")
end

This can be used as follows:

{:ok, pid} = GenFRP.start_link(GenFRP.Example.Map)
# ... maybe some other code here...
GenFRP.send_event(pid, {:foo, :bar})
# ... maybe some more code here...
GenFRP.send_event(pid, {:baz, 42})
# ... maybe yet some other code here...
GenFRP.render(pid)
"`foo`: `bar`
`baz`: `42`
"

Installation

The package can be installed by adding gen_frp to your list of dependencies in mix.exs:

def deps do
  [{:gen_frp, "~> 0.5.0"}]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/gen_frp.

Changelog

• 0.5.0 Changed the way the initial state works to init/0, to follow the naming convention that GenServer et al. already use. Also, documentation was improved.
• 0.1.0 Initial released version.