GenClient

GenClient is an elixir library made to generate boilerplate code that I found myself repeatedly writing and changing when working with GenServers.

Every time I wanted to add or remove a parameter from a GenServer module I needed to do so in several places.

GenClient is a metaprogramming library that helps the programmer write their logic in a single location and keep it there.

Example

Here is a module written using a standard GenServer implementation

counter.ex

defmodule Counter do
  defdelegate increment(pid), to: Client
  defdelegate peek(pid),      to: CLient
end

counter/client.ex

defmodule Counter.Client do

  def increment() do
    GenServer.cast(pid. :increment)
  end

  def peek() do
    GenServer.call(pid, :peek)
  end

end

counter/server.ex

defmodule Counter.Server do
  def handle_cast(:increment, state) do
    {:no_reply, Counter.Impl.increment(state)}
  end

  def handle_call(:peek, _from, state) do
    {:reply, state, state}
  end
end

counter/impl.ex

defmodule Counter.Impl do
  def increment(state), do: state + 1
end

The Previous Module Can be written using GenClient as follows:

counter.ex

defmodule Counter do
  use GenClient,
    for: Counter.Impl,
    calls: [:peek],
    casts: [:increment, :increment_by]
end

counter/counter.impl.ex

defmodule Counter.Impl do
  def increment(state), do: state + 1
  def peek(state) do state
    result = state + 1
    response = result
    {response, result}
  end
end

The resulting api will be exactly the same

Adding as a mix dependency

  def deps do
    [{:gen_client, git:"https://github.com/LukeWood/GenClient"}]
  end