# DefinedBy

> Advanced DSL and Dynamic class generation for Ruby

## When do I is this?

- If you want to use a DSL to cut down on your code base
- If you need that DSL to create classes
- If you have a base class (e.g. `Widget`) and want to subclass it dozens of times but it's overkill to create separate classes for it manually.
- Define template classes (default values for subclasses)
    
## All at once    
    
    class Widget
      class << self
        def define(&block)
          DefinedBy::DSL(&block).map do |key, value, dsl_block|
            define_class(key, self).new(:name => key.to_s, :description => value)
          end
        end
      end
      
      attr_accessor :name, :description

      def initialize(attributes = {})
        attributes.each do |key, value|
          self.send("#{key.to_s}=", value)
        end
      end
    end
    
    def Widget(&block)
      Widget.define(&block)
    end

    widgets = Widget do
      widget_a "This widget does X"
      widget_b "This does Y"
    end

    puts widgets.inspect
    #=> [
      #<WidgetA:0x5c3348 @description="This widget does X", @name="widget_a">,
      #<WidgetB:0x5c2970 @description="This does Y", @name="widget_b">
    ]
    
http://www.khelll.com/blog/ruby/stackoverflow-cool-ruby-questions-4/