Define elixir structs with typespec with single line of code

box.ex

defmodule Box do
  defmacro __using__(_env) do
    quote do
      import Box
    end
  end

  @doc """
  Define module with struct and typespec, in single line

  Example:

      use Box
      defbox User,  id:   integer,
                    name: String.t

  is the same as

      defmodule User do
        @type t :: %__MODULE__{
          id:   integer,
          name: String.t
        }

        @enforce_keys [:id, :name]
        defstruct [:id, :name]
      end
  """
  defmacro defbox(name, attrs \\ []) do
    keys = Keyword.keys(attrs)

    quote do
      defmodule unquote(name) do
        @enforce_keys unquote(keys)
        defstruct unquote(keys)
        @type t :: %__MODULE__{
          unquote_splicing(attrs)
        }
      end
    end
  end
end

example.ex

# Instead of long definition of module
# with struct & typespec & enforce_keys ...
defmodule One do
  defmodule User do
    @type t :: %__MODULE__{
      id:   integer,
      name: String.t
    }

    @enforce_keys [:id, :name]
    defstruct [:id, :name]
  end

  defmodule Company do
    @type t :: %__MODULE__{
      id:     integer,
      name:   String.t,
      domain: String.t,
      rating: float
    }

    @enforce_keys [:id, :name, :domain, :rating]
    defstruct [:id, :name, :domain, :rating]
  end

  defmodule Account do
    @type t :: %__MODULE__{
      user:    User.t,
      company: Company.t
    }

    @enforce_keys [:user, :company]
    defstruct [:user, :company]
  end
end


# ... define all that in much more concise way
defmodule Two do
  # include the Box library
  use Box

  # use defbox to define modules and structs
  # in a single line of code


  defbox User,  id:   integer,
                name: String.t

  defbox Company, id:     integer,
                  name:   String.t,
                  domain: String.t,
                  rating: float

  defbox Account, user:    User.t,
                  company: Company.t
end