class Thor::Group

def invoke_from_option(*names, &block)


class and the klass to be invoked.
invoked. The block receives two parameters, an instance of the current
You can also supply a block to customize how the option is going to be

==== Custom invocations

and an optional task.
prepare_for_invocation. The class method must necessarily return a klass
invoked. You can do that by overwriting the class method
In some cases you want to customize how a specified hook is going to be

==== Preparing for invocation

option name is used to invoke the generator.
false. This is automatically handled by invoke_from_option. Then the
In some cases, you want to invoke a thor class if some option is true or

==== Boolean options

end
invoke_from_option :test_framework
class_option :test_framework, :type => :string
class GemGenerator < Thor::Group

==== Examples

method is invoked for each name given.
given option named "name". A class option must be created before this
Invoke a thor class based on the value supplied by the user to the 
def invoke_from_option(*names, &block)
  options = names.last.is_a?(Hash) ? names.pop : {}
  verbose = options.fetch(:verbose, :white)
  names.each do |name|
    unless class_options.key?(name)
      raise ArgumentError, "You have to define the option #{name.inspect} " <<
                           "before setting invoke_from_option."
    end
    invocations[name] = true
    invocation_blocks[name] = block if block_given?
    class_eval <<-METHOD, __FILE__, __LINE__
      def _invoke_from_option_#{name.to_s.gsub(/\W/, '_')}
        return unless options[#{name.inspect}]
        value = options[#{name.inspect}]
        value = #{name.inspect} if TrueClass === value
        klass, task = self.class.prepare_for_invocation(#{name.inspect}, value)
        if klass
          say_status :invoke, value, #{verbose.inspect}
          block = self.class.invocation_blocks[#{name.inspect}]
          _invoke_for_class_method klass, task, &block
        else
          say_status :error, %(\#{value} [not found]), :red
        end
      end
    METHOD
  end
end