gistfile1.rb

# ----------------------------------------------------------------
# Injecting reloadable code into a rails core class from a plugin
# ----------------------------------------------------------------

# lib/action_view_extensions/foo_form_helper.rb

module ActionViewExtensions::FooFormHelper
  def foo
    "foo!"
  end
  def bar
    "bar!"
  end
end

# init.rb

# This injects code into ActionView::Base which allows my extensions to be
# reloaded even though ActionView::Base isn't.
ext = ActionViewExtensions::FooFormHelper
ActionView::Base.class_eval %{
  def method_missing_with_foo_extensions(method, *args, &block)
    unless extended_by.include?(#{ext})     # skip if already extended
      extend(#{ext})                        # extend with module
      if respond_to?(method)                # check again
        return send(method, *args, &block)  # A.O.K, call it and go
      end
    end
    # fall back otherwise
    method_missing_without_foo_extensions(method, *args, &block)
  end
  alias_method_chain :method_missing, :foo_extensions
}