How to properly implement dynamic dispatch?

Questions & Help Questions
5

Ok…

so if I have a behavior like:

defmodule X 
@callback one(any) :: integer 
@callback two(any) :: integer
end

How do I achieve a pattern like “I want to write a function that an implementor of this behavior will get by default”? I was trying:

defmodule X 
@callback one(any) :: integer
@callback two(any) :: integer
def three(o, t) do one(o) + two(t) end
end

This is not right because behaviors don’t work like that… I have to use the using macro:

defmodule X 
@callback one(any) :: integer
@callback two(any) :: integer
defmacro __using__ do
  def three(o, t) do one(o) + two(t) end
end
end

Then I would use X instead of @behavior X so that I get the extra code that I want.
Is that correct? Is there a better way of doing this?