Why error -- undefined function defstruct

Question

I have this modules where I'm trying to define a struct:

defmodule A do
  defmodule B do
    defstruct :id, :name
  end
end

Why error?

undefined function defstruct/2

Why is this error?

Answer 1

Elixir interprets defstruct :id, :name as calling defstruct with 2 arguments, that's the /2 part in undefined function defstruct/2.

What you want to do is pass a single argument to defstruct, a list of field names:

defmodule A do
  defmodule B do
    defstruct [:id, :name]
  end
end