How to use any cucumber step as a scoped step

selectors.rb

# Add selector mappings here, any selector in the format "..." is treated as raw css
#
module SelectorsHelper
  include ActionController::RecordIdentifier
  
  def selector_for(selector)
    case selector
    
    when /^"(.*)"$/
      $1
    
    # example mappings form phrases to selectors
    when "my cart"
      'div#cart'
    
    # active record
    when /^the user "(.*)"$/
      '#' + dom_id(User.find_by_login($1))
    
    # pickle
    when /^#{capture_model}$/
      '#' + dom_id(model!($1))

    else
      raise "Can't convert #{selector} to a css selector.  Use quotes if giving a straight css selector"
      
    end
  end
end
 
World(SelectorsHelper)

within_steps.rb

# Allow all cucumber steps to be reused as scoped steps, and enable human friendly
# interpretation of selectors.  
#
# Found at: http://gist.github.com/gists/239570 - Ian White & Nick Rutherford, Nov 2009
#
# to enable these steps:
#
# the default 'webrat_steps.rb' must
#   * have 'response' replaced by 'current_dom'
#   * all 'within' steps removed
#
# you should have support/selectors.rb installed
 
# This allows steps like
#
#   When I press "foo" within "div.panel"
#   Then I should see "Total: £20" in my cart
#
register_rb_step_definition(/^(.+?) within (.+?)$/) do |step, selector|
  within(selector_for(selector)) { __cucumber_invoke step }
end
 
# This allows steps like
#
#   When within the product's panel:
#     | I fill in "Price" with "$100" |
#     | I press "Submit"              |
#
register_rb_step_definition(/^within (.+?):?$/) do |selector, table|
  steps = table.raw.flatten
  within(selector_for(selector)) { steps.each {|step| __cucumber_invoke step } }
end