Rails - Jun 2009 - Polymorphism question

I am setting up a tagging system using polymorphism and it works about
half the way I would expect it to.  One thing in my app that can be
tagged is blogs.  I am able to tag them and it works as I expect when I
save the blog and when I call blog.tags it returns the list of tags
associated with that blog.  The thing that does not work is when I am
trying to display a list of all the blogs for a certain tag.  For
example:

tag = Tag.find(1)
tag.blogs ## => returns nil

Here is my setup:

class Tag < ActiveRecord::Base
end

class Tagging < ActiveRecord::Base
  belongs_to :tag
  belongs_to :taggable, :polymorphic => true
end

class Blog < ActiveRecord::Base
  has_many :taggings, :as => :taggable
  has_many :tags, :through => :taggings
end

##when I save a blog in my controller, I do this to assign a tag to it
blog = Blog.find(1)
tagging = Tagging.new(:tag_id=>tag_id)
tagging.taggable = blog
tagging.save

I have tried experimenting with all kinds of things in the Tag model
(ex: has_many :blogs, :through =>:taggings), but nothing seems to work.
What am I missing?  Maybe I am misunderstanding how polymorphism works
or maybe there is a better way to set this up in general.

Thanks in advance!
John
-- 
Posted via http://www.ruby-forum.com/.

One of the existing plugins such as acts_as_taggable_on_steroids might
have this functionality already... I''m not sure though.

Here''s one way to do it:

class Blog < ActiveRecord::Base
  has_many :taggings, :as => :taggable
  has_many :tags, :through => :taggings
end

class Tagging < ActiveRecord::Base
  belongs_to :tag
  belongs_to :taggable, :polymorphic => true
end

class Tag < ActiveRecord::Base
  has_many :taggings

  def get(taggable)
    self.taggings.all(:conditions => ["taggable_type = ?",
taggable.to_s.singularize.camelize]).map(&:taggable)
  end
end
require ''test_helper''

class TagTest < ActiveSupport::TestCase

  test ''should get taggable type'' do
    tag = Tag.create(:name => ''blogtag'')
    blog1 = Blog.create(:name => ''blog1'')
    blog1.tags << tag
    blog2 = Blog.create(:name => ''blog2'')
    blog2.tags << tag

    assert_equal [tag], blog1.tags
    assert_equal [blog1, blog2], tag.get(:blogs)
  end

end

Hello Yanni mac,

You can use acts-as-taggable-on plugin for same purpose.

Cheers !
Sandip

On Wed, Jun 3, 2009 at 8:22 PM, jemminger
<jemminger-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>
> One of the existing plugins such as acts_as_taggable_on_steroids might
> have this functionality already... I''m not sure though.
>
> Here''s one way to do it:
>
> class Blog < ActiveRecord::Base
>  has_many :taggings, :as => :taggable
>  has_many :tags, :through => :taggings
> end
>
> class Tagging < ActiveRecord::Base
>  belongs_to :tag
>  belongs_to :taggable, :polymorphic => true
> end
>
> class Tag < ActiveRecord::Base
>  has_many :taggings
>
>  def get(taggable)
>    self.taggings.all(:conditions => ["taggable_type = ?",
> taggable.to_s.singularize.camelize]).map(&:taggable)
>  end
> end
> require ''test_helper''
>
> class TagTest < ActiveSupport::TestCase
>
>  test ''should get taggable type'' do
>    tag = Tag.create(:name => ''blogtag'')
>    blog1 = Blog.create(:name => ''blog1'')
>    blog1.tags << tag
>    blog2 = Blog.create(:name => ''blog2'')
>    blog2.tags << tag
>
>    assert_equal [tag], blog1.tags
>    assert_equal [blog1, blog2], tag.get(:blogs)
>  end
>
> end
>
> >
>

-- 
Ruby on Rails Developer
http://sandip.sosblog.com
http://funonrails.wordpress.com
www.joshsoftware.com

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