convertible.ex

convertible.ex

defprotocol Convertible do
  def convert(a, target_struct)
end

defmodule ConversionBoilerplate do
  defmacro __using__() do
    quote do
      def convert(a, to: struct_module) do
        # maybe do some asserts here
        module = Module.concat(__MODULE__, struct_module)
        if function_exported?(module, :convert, 1) do
          module.convert(a)
        else
          raise "arglebargle"
        end
      end
    end
  end
  
  defmacro defconvertible(module) do
    quote do
      defimpl Convertible, for: unquote(module) do
        use ConversionBoilerplate
      end
    end
  end
end

import ConversionBoilerplate
defconvertible A

defmodule A.B do
  def convert(a) do
    ...
  end
end