Access project version within elixir application

Mix.Project itself provides access to all project keywords defined in mix.exs using its config/0 (api doc) function. For concise access it might be wrapped into a function:

@version Mix.Project.config[:version]
def version(), do: @version

I found the version inside of :application.which_applications, but it requires some parsing:

defmodule AppHelper do
  @spec app_version(atom) :: {integer, integer, integer}
  def app_version(target_app) do
    :application.which_applications
    |> Enum.filter(fn({app, _, _}) ->
                    app == target_app
                   end)
    |> get_app_vsn
  end

  # I use a sensible fallback when we can't find the app,
  # you could omit the first signature and just crash when the app DNE.
  defp get_app_vsn([]), do: {0,0,0} 
  defp get_app_vsn([{_app, _desc, vsn}]) do
    [maj, min, rev] = vsn
                      |> List.to_string
                      |> String.split(".")
                      |> Enum.map(&String.to_integer/1)
    {maj, min, rev}
  end
end

And then for usage:

iex(1)> AppHelper.app_version(:logger)
{1, 0, 5}

As always, there's probably a better way.

Here's a similar approach to retrieve the version string. It also relies on the :application module, but is maybe a bit more straightforward:

{:ok, vsn} = :application.get_key(:my_app, :vsn)
List.to_string(vsn)

In recent versions of Elixir, the Application module now wraps this for you:

https://github.com/elixir-lang/elixir/blob/master/lib/elixir/lib/application.ex

Application.spec(:my_app, :vsn) |> to_string()

The Kernel.to_string() method is necessary as Application.spec/2 for the keys :vsn and :description return charlists. to_string() from the Kernel module converts them to a binary.