Rails - Jun 2006 - How can I dynamiclly generate models?

I am trying to write a plugin, ''acts_as_commentable'', for my
models -
Image, Book, Music and so on, I do not want to use polymorphic 
association, so very model should have its own comment class.
Here is my code

acts_as_commentable.rb
module Commentable

    def self.included(base)
        base.extend(ClassMethods)
    end

    module ClassMethods
        def acts_as_commentable(options = {})
            class_def = "class Comment < ActiveRecord::Base
                set_table_name
''#{self.name.downcase}_comments''

                belongs_to :user, :class_name=>''::User''
                belongs_to :#{self.name.downcase}, 
:class_name=>''::#{self}''
            end"
            self.class_eval class_def

            has_many :comments,
:class_name=>"#{self.name}::Comment",
:order=>''created_at desc'', :dependent => :delete_all

            extend Commentable::SingletonMethods
            include Commentable::InstanceMethods
        end
    end

    module SingletonMethods
    end

    module InstanceMethods
    end

end

init.rb
require ''acts_as_commentable''
ActiveRecord::Base.send(:include, Commentable)

image.rb
acts_as_commentable

This results in Image::Comment, Book::Comment...(I have no idea about 
how defind top level classes ImageComment, BookComment... :( )

and my controller:
def ImageController
  def view
    ...
    @comment=Event::Comment.new  #line 45
    ...
  end
end

everything is ok when I start webrick and direct to this page, but when 
I refresh my brower, an error ocurr:
NameError in ImageController#view
uninitialized constant Comment
c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/active_support/dependencies.rb:100:in
`const_missing''
c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/active_support/dependencies.rb:131:in
`const_missing''
c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/active_support/dependencies.rb:133:in
`const_missing''
#{RAILS_ROOT}/app/controllers/image_controller.rb:45:in `view''

Anyone know what''s the problem, thanks in advance ^_^


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Image.find(1).comments() and Image::Comment.new work in the console.

It seems people like generating model methods/attrs much more than 
generating the whole model classes :(

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I add

def self.reloadable?
  false
end

to the Comment class definition, it works now :)
and I find

class ::ImageComment
end

defines a top level class...

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Hey,

I synthesize classes in my acts_as_enumerated plugin.  You can see  
how I do it here:

http://svn.protocool.com/rails/plugins/enumerations_mixin/trunk/lib/ 
active_record/virtual_enumerations.rb

In the "synthesize_if_defined" method I create the toplevel class  
like this:

eval(class_def, TOPLEVEL_BINDING)

Hope this helps,
Trevor
--
Trevor Squires
http://somethinglearned.com



On 26-Jun-06, at 7:46 AM, cafe babe wrote:
> I am trying to write a plugin, ''acts_as_commentable'', for
my models -
> Image, Book, Music and so on, I do not want to use polymorphic
> association, so very model should have its own comment class.
> Here is my code
>
> acts_as_commentable.rb
> module Commentable
>
>     def self.included(base)
>         base.extend(ClassMethods)
>     end
>
>     module ClassMethods
>         def acts_as_commentable(options = {})
>             class_def = "class Comment < ActiveRecord::Base
>                 set_table_name
''#{self.name.downcase}_comments''
>
>                 belongs_to :user,
:class_name=>''::User''
>                 belongs_to :#{self.name.downcase},
> :class_name=>''::#{self}''
>             end"
>             self.class_eval class_def
>
>             has_many :comments,
:class_name=>"#{self.name}::Comment",
> :order=>''created_at desc'', :dependent =>
:delete_all
>
>             extend Commentable::SingletonMethods
>             include Commentable::InstanceMethods
>         end
>     end
>
>     module SingletonMethods
>     end
>
>     module InstanceMethods
>     end
>
> end
>
> init.rb
> require ''acts_as_commentable''
> ActiveRecord::Base.send(:include, Commentable)
>
> image.rb
> acts_as_commentable
>
> This results in Image::Comment, Book::Comment...(I have no idea about
> how defind top level classes ImageComment, BookComment... :( )
>
> and my controller:
> def ImageController
>   def view
>     ...
>     @comment=Event::Comment.new  #line 45
>     ...
>   end
> end
>
> everything is ok when I start webrick and direct to this page, but  
> when
> I refresh my brower, an error ocurr:
> NameError in ImageController#view
> uninitialized constant Comment
> c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/ 
> active_support/dependencies.rb:100:in
> `const_missing''
> c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/ 
> active_support/dependencies.rb:131:in
> `const_missing''
> c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/ 
> active_support/dependencies.rb:133:in
> `const_missing''
> #{RAILS_ROOT}/app/controllers/image_controller.rb:45:in `view''
>
> Anyone know what''s the problem, thanks in advance ^_^
>
>
> -- 
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails

>
> eval(class_def, TOPLEVEL_BINDING)
>
This is very much appreciated.  Thank you!

-- 
Andrew Stone
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thanks
this following code also works

class OuterClass
    ....
    class_eval "class ::TopLevelCalss
    end
    "
    ...
end

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