Rails - Jun 2006 - Macros and stuff

I was looking at my controller code and the edit/create/update/new for 
each are practically identical. So first I DRY''d the four methods in 
each controller to just one and then I decided to write a single macro 
for all my controllers.

This is the macro:

  def self.edit_action_for(model, options = {})
    model_class = Object.const_get(model)
    define_method(:edit) do
      edit_code = lambda do
        @thing = model_class.find_by_id(params[:id]) || model_class.new
        if request.post?
          @thing.attributes = params[:impactable_area]
          if @thing.save
            flash[:notice] = "#{model.humanize} successfully saved."
            redirect_to :action => ''list''
          end
        end
      end
    end
  end

Then I expected this

  edit_action_for :ImpactableArea

to create my "edit" method.

Problem is that it doesn''t :-(

So then I looked to see how I could do a macro expansion (as you can in 
Lisp) to see what''s being produced and I couldn''t find
anything...

HELP!

Edward

-- 
Posted via http://www.ruby-forum.com/.

The problem is that you''re not actually adding a new method definition
to the class when you call "edit_action_for" -  you''re just
calling a
class method. Basically you''re doing this:

  class Blah
    def self.test
       # do something
       # return something maybe?
       return ''hello!'' # in this case
    end
    # now call this
    test
  end

  ==> ''hello!''

... not what you want. In your abstracted-out class method, you
actually want to be creating a new method to be added to the class
definition in which your macro is being called. You probably want to
investigate the delightful intricacies of define_method and
eval/class_eval - welcome to metaprogamming...

- james

On 6/8/06, Edward Kenworthy <edward@kenworthy.info>
wrote:
> I was looking at my controller code and the edit/create/update/new for
> each are practically identical. So first I DRY''d the four methods
in
> each controller to just one and then I decided to write a single macro
> for all my controllers.
>
> This is the macro:
>
>   def self.edit_action_for(model, options = {})
>     model_class = Object.const_get(model)
>     define_method(:edit) do
>       edit_code = lambda do
>         @thing = model_class.find_by_id(params[:id]) || model_class.new
>         if request.post?
>           @thing.attributes = params[:impactable_area]
>           if @thing.save
>             flash[:notice] = "#{model.humanize} successfully
saved."
>             redirect_to :action => ''list''
>           end
>         end
>       end
>     end
>   end
>
> Then I expected this
>
>   edit_action_for :ImpactableArea
>
> to create my "edit" method.
>
> Problem is that it doesn''t :-(
>
> So then I looked to see how I could do a macro expansion (as you can in
> Lisp) to see what''s being produced and I couldn''t find
anything...
>
> HELP!
>
> Edward
>
> --
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>

-- 
* J *
  ~

James Adam wrote:
> <snip>
> ... not what you want. In your abstracted-out class method, you
> actually want to be creating a new method to be added to the class
> definition in which your macro is being called. You probably want to
> investigate the delightful intricacies of define_method and
> eval/class_eval - welcome to metaprogamming...
> 
> - james
Think you may have misread my code. Have a look at Line 2 of 
edit_action_for

define_method(:edit) do

Edward


-- 
Posted via http://www.ruby-forum.com/.

You''re absolutely right. Hopefully this will help me pay penance for
my illiteracy:

class Blah
  def self.new_thing(arg)
    define_method(:do_it!) do
      puts "ok: #{arg}"
    end
  end

  new_thing "monkey"
end

b = Blah.new
b.do_it!

# ==> ok: monkey

module Mung
  def self.new_thing(arg)
    define_method(:do_it!) do
      puts "ok: #{arg}"
    end
  end
end

class Jazz
  include Mung

  new_thing "baboon"
end

j = Jazz.new
j.do_it!

# ==>  undefined method `new_thing'' for Jazz:Class (NoMethodError)

module Soul
  def self.included(base)
    base.extend(ClassMethods)
  end
  module ClassMethods
    def new_thing(arg)
      define_method(:do_it!) do
        puts "Hit it; #{arg}"
      end
    end
  end
end

class Funk
  include Soul

  new_thing "Watch me now!"
end

f = Funk.new
f.do_it!

# ==> Hit it; Watch me now!

- james

On 6/8/06, Edward Kenworthy <edward@kenworthy.info>
wrote:
> James Adam wrote:
> > <snip>
> > ... not what you want. In your abstracted-out class method, you
> > actually want to be creating a new method to be added to the class
> > definition in which your macro is being called. You probably want to
> > investigate the delightful intricacies of define_method and
> > eval/class_eval - welcome to metaprogamming...
> >
> > - james
>
> Think you may have misread my code. Have a look at Line 2 of
> edit_action_for
>
> define_method(:edit) do
>
> Edward
>
>
> --
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>

-- 
* J *
  ~