acts_as_nested_set

# File activerecord/lib/active_record/acts/nested_set.rb, line 81
        def acts_as_nested_set(options = {})
          configuration = { :parent_column => "parent_id", :left_column => "lft", :right_column => "rgt", :scope => "1 = 1" }
          
          configuration.update(options) if options.is_a?(Hash)
          
          configuration[:scope] = "#{configuration[:scope]}_id".intern if configuration[:scope].is_a?(Symbol) && configuration[:scope].to_s !~ /_id$/
          
          if configuration[:scope].is_a?(Symbol)
            scope_condition_method = %(
              def scope_condition
                if #{configuration[:scope].to_s}.nil?
                  "#{configuration[:scope].to_s} IS NULL"
                else
                  "#{configuration[:scope].to_s} = \#{#{configuration[:scope].to_s}}"
                end
              end
            )
          else
            scope_condition_method = "def scope_condition() \"#{configuration[:scope]}\" end"
          end
        
          class_eval "include ActiveRecord::Acts::NestedSet::InstanceMethods\n\n\#{scope_condition_method}\n\ndef left_col_name() \"\#{configuration[:left_column]}\" end\n\ndef right_col_name() \"\#{configuration[:right_column]}\" end\n\ndef parent_column() \"\#{configuration[:parent_column]}\" end\n\n"
        end