Options in command line in scaffold generations

I write:
./script/generate manage_scaffold product PARENT=structure

but, when I try to use ENV['PARENT'] it always is nil value.
How can I get parameter value from option in command line, when
scaffold is generating model?

P.S. "manage_scafold" is my owner plugin:

require 'rails_generator/generators/components/scaffold/
scaffold_generator'

class ManageScaffoldGenerator < ScaffoldGenerator

ARGV return array, but it don't fit me, becouse I have many other
parameters - [field:Type, field:Type]