Robert Klemme wrote: >> How to write the line correct? > > This should work: > > cl.class_eval "include 'DrgReports#{opts[:format]}'" > > But again, inclusion - which is a special form of inheritance - does > not seem the proper technique here. > > Kind regards > > robert Thanks this works now. I had to leave out single quotes. def run_report(source_file, opts={}, default_opts={}) opts[:format] ||= 'HTML' load source_file + '.rb' cl = Object.const_get File.basename(source_file).capitalize cl.class_eval "include DrgReports#{opts[:format]}" report = cl.class_eval 'new' report.set_options(default_opts) report.set_options(opts) report.create report.do_report report.close end It looks nicer and I understand a piece of Ruby a little more. I will try to study delegation this weekend. by TheR -- Posted via http://www.ruby-forum.com/.