auto_complete plugin

I have a method in my controller that would apply to all fields that
use the auto_complete plugin

  def auto_complete_for

    object = params[:id].split('_')[0]
    method = params[:id].split('_')[1]

    table = object.to_s.camelize.constantize.table_name

    object.to_s.camelize.constantize::init( @lang )
    tables = object.to_s.camelize.constantize::tables

    if tables.include?( "#{table}_#{method}" )

  etc...

So in my template I have:

<%=text_field_with_auto_complete :sample, c, {:skip_style=>true} %>

but the ajax request is not right. It says

http://localhost:3000/echantillons/auto_complete_for_sample_technique

and the parameters are
Parameters: {"sample"=>{"technique"=>"test"}}

whereas I think it should say

http://localhost:3000/echantillons/auto_complete_for/sample_technique
with parameters {"id"=>{"sample_technique""}}

What am I doing wrong?