[erlang-questions] Parameterized module and behaviour undefined warning.

[Richard Carlsson]

Kenny MacDermid wrote:
> I wondering if I should be using '-behaviour()' differently for a 
> parameterized module. I'm getting "Warning: behaviour ____ undefined".
> 
> Here's the module that I'm using as the behaviour:
> 
> -----
> -module(prmmodule, [Param1, Param2]).
> 
> -export([behaviour_info/1]).
> 
> behaviour_info(callbacks) ->
>   [{a, 1}, {b, 1}].
> -----

The implementation of parameterized modules does not currently
know to treat behaviour_info/1 as a special "static" function,
so it will add an extra argument for the current module instance.
This causes a warning, since the compiler does not find the
expected behaviour_info/1 in prmmodule.

The workaround is to make a separate, non-parameterized module
containing as a facade to the parameterized one, and put the
behaviour declaration in that one instead.

     /Richard