Generators

# If we load in the generator this way it will *always* be loaded

scope "merb-gen" do
  Merb.add_generators File.join(File.dirname(__FILE), 'lib', 'generators', 'model')
end

merb_datamapper.rb

# normal stuff
require ...

# if we load in the generator this way, it will only be loaded if merb_datamapper is a dependency in the application
Merb.add_generators File.join(File.dirname(__FILE), 'generators', 'model')

model.rb

module Merb::Generators
  class DatamapperModelGenerator < ComponentGenerator

    # do stuff here
    template ...

  end

  # this thing should be invisible to the end user, since it will never be called
  # directly
  add_private :datamapper_model
end

# The model generator invokes the datamapper_model generator if
# the orm is set to :datamapper
Merb::Generators::ModelGenerator.invoke :datamapper_model, :orm => :datamapper