Am I reinventing polymorphic associations? I have a fairly standard blog with comments model, with the following additions: (1) Multiple models can accept comments (blog post, bug report, etc). (2) Each group of comments has a list of subscribers that will be emailed when a new comment is posted. Requirement (1) leads me to a polymorphic association. But I can''t see how to fit requirement (2) into that. Each group of comments needs some place to store the list of subscribers. So I added a CommentGroup table. class BlogPost < ActiveRecord::Base belongs_to :comment_group end class BugReport < ActiveRecord::Base belongs_to :comment_group end class CommentGroup < ActiveRecord::Base has_one :blog_post has_one :bug_report # note: one or the other will be nil has_and_belongs_to_many :subscribers end class Comment < ActiveRecord::Base belongs_to :comment_group end ---- But now table :comment_group only has one field: id. And that just seems wrong to me. Is that bad?
I think you are. I''d make Comment polymorphic, a nested set, and has_many :subscribers, which should be based on the top parent of the comment thread. -eric On Oct 15, 4:32 pm, Scott Johnson <sc...-wIW8SF+lElu2kH9Ulgv/9g@public.gmane.org> wrote:> Am I reinventing polymorphic associations? > > I have a fairly standard blog with comments model, with the following > additions: > > (1) Multiple models can accept comments (blog post, bug report, etc). > > (2) Each group of comments has a list of subscribers that will be > emailed when a new comment is posted. > > Requirement (1) leads me to a polymorphic association. But I can''t see > how to fit requirement (2) into that. Each group of comments needs > some place to store the list of subscribers. > > So I added a CommentGroup table. > > class BlogPost < ActiveRecord::Base > belongs_to :comment_group > end > > class BugReport < ActiveRecord::Base > belongs_to :comment_group > end > > class CommentGroup < ActiveRecord::Base > has_one :blog_post > has_one :bug_report # note: one or the other will be nil > > has_and_belongs_to_many :subscribers > end > > class Comment < ActiveRecord::Base > belongs_to :comment_group > end > ---- > > But now table :comment_group only has one field: id. And that just > seems wrong to me. > > Is that bad?
A nested set seems a little overkill. I realized I could make two polymorphic associations: one in Comments, and one in the join table for commentable_subscribers. I''m not sure if that''s a better plan or not, though. I like that I can enforce foreign key constraints when I use the extra CommentGroup table. On Oct 15, 6:49 pm, Eric <ericgh...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> I think you are. I''d make Comment polymorphic, a nested set, and > has_many :subscribers, which should be based on the top parent of the > comment thread. > > -eric > > On Oct 15, 4:32 pm, Scott Johnson <sc...-wIW8SF+lElu2kH9Ulgv/9g@public.gmane.org> wrote: > > > Am I reinventing polymorphic associations? > > > I have a fairly standard blog with comments model, with the following > > additions: > > > (1) Multiple models can accept comments (blog post, bug report, etc). > > > (2) Each group of comments has a list of subscribers that will be > > emailed when a new comment is posted. > > > Requirement (1) leads me to a polymorphic association. But I can''t see > > how to fit requirement (2) into that. Each group of comments needs > > some place to store the list of subscribers. > > > So I added a CommentGroup table. > > > class BlogPost < ActiveRecord::Base > > belongs_to :comment_group > > end > > > class BugReport < ActiveRecord::Base > > belongs_to :comment_group > > end > > > class CommentGroup < ActiveRecord::Base > > has_one :blog_post > > has_one :bug_report # note: one or the other will be nil > > > has_and_belongs_to_many :subscribers > > end > > > class Comment < ActiveRecord::Base > > belongs_to :comment_group > > end > > ---- > > > But now table :comment_group only has one field: id. And that just > > seems wrong to me. > > > Is that bad?
Scott Johnson wrote:> A nested set seems a little overkill.It''s not overkill at all if you''re threading your comments.> > I realized I could make two polymorphic associations: one in Comments, > and one in the join table for commentable_subscribers. > > I''m not sure if that''s a better plan or not, though. I like that I can > enforce foreign key constraints when I use the extra CommentGroup > table.Why not keep CommentGroup and have a polymorphic association that will bind it to either BlogPost or BugReport? Best, -- Marnen Laibow-Koser http://www.marnen.org marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org -- Posted via http://www.ruby-forum.com/.
On Oct 16, 8:43 am, Marnen Laibow-Koser <rails-mailing-l...@andreas- s.net> wrote:> Scott Johnson wrote: > > A nested set seems a little overkill. > > It''s not overkill at all if you''re threading your comments.Good point, and I hadn''t thought of that, but I don''t need nesting.> > I realized I could make two polymorphic associations: one in Comments, > > and one in the join table for commentable_subscribers. > > > I''m not sure if that''s a better plan or not, though. I like that I can > > enforce foreign key constraints when I use the extra CommentGroup > > table. > > Why not keep CommentGroup and have a polymorphic association that will > bind it to either BlogPost or BugReport?That sounds like the best plan. Thanks for the help.
I ended up refactoring this to remove CommentGroup. The controller
code for CommentGroup was too ugly.
Here''s how my associations ended up:
class User < ActiveRecord::Base
has_many :subscriptions
end
class Comment < ActiveRecord::Base
belongs_to :author, :class_name => "User"
belongs_to :commentable, :polymorphic => true
end
class Subscription < ActiveRecord::Base
belongs_to :subscribable, :polymorphic => true
belongs_to :user
end
class BlogPost < ActiveRecord::Base
has_many :subscriptions, :as => :subscribable
has_many :subscribers, :through => :subscriptions, :source => :user
has_many :comments, :as => :commentable
end
Subscribable and Commentable are basically the same thing.
Then I added routes that appear as nested routes for any of the
commentable/subscribable types:
map.comments(":commentable_type/:commentable_id/comments",
:controller => :comments,
:action => :create,
:conditions => {:method => :post}
)
map.subscribers(":subscribable_type/:subscribable_id/subscribers",
:controller => :subscribers,
:action => :update,
:conditions => {:method => :post}
)
map.subscribers_table(":subscribable_type/:subscribable_id/
subscribers/table",
:controller => :subscribers,
:action => :table,
:conditions => {:method => :get}
)
Then I have controllers and views for Comments and Subscribers that
operate on commentable or subscribable and don''t care what type they
are.
To enable an additional model class as commentable (and subscribable)
I just add the three has_many lines (like BlogPost), and add the
comments partial to the appropriate view.
Next: how can I DRY up those three has_many lines? I want to put
something like ''acts_as_commentable'' in the model and have it
do those
three has_many lines.
On Oct 16, 10:31 am, Scott Johnson
<sc...-wIW8SF+lElu2kH9Ulgv/9g@public.gmane.org>
wrote:> On Oct 16, 8:43 am, Marnen Laibow-Koser <rails-mailing-l...@andreas-
>
> s.net> wrote:
> > Scott Johnson wrote:
> > > A nested set seems a little overkill.
>
> > It''s not overkill at all if you''re threading your
comments.
>
> Good point, and I hadn''t thought of that, but I don''t
need nesting.
>
> > > I realized I could make two polymorphic associations: one in
Comments,
> > > and one in the join table for commentable_subscribers.
>
> > > I''m not sure if that''s a better plan or not,
though. I like that I can
> > > enforce foreign key constraints when I use the extra CommentGroup
> > > table.
>
> > Why not keep CommentGroup and have a polymorphic association that will
> > bind it to either BlogPost or BugReport?
>
> That sounds like the best plan. Thanks for the help.
Scott Johnson wrote: [...]> Next: how can I DRY up those three has_many lines? I want to put > something like ''acts_as_commentable'' in the model and have it do those > three has_many lines.Define it as an ActiveRecord::Base class method. Best, -- Marnen Laibow-Koser http://www.marnen.org marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org -- Posted via http://www.ruby-forum.com/.
On Oct 23, 11:11 am, Marnen Laibow-Koser <rails-mailing-l...@andreas- s.net> wrote:> Define it as an ActiveRecord::Base class method.Sure, but where? In lib/* somewhere? I''ll need it to get loaded before any of these models get loaded. (Or I would have to add a ''require'' to each commentable model.)
Scott Johnson wrote:> On Oct 23, 11:11 am, Marnen Laibow-Koser <rails-mailing-l...@andreas- > s.net> wrote: >> Define it as an ActiveRecord::Base class method. > > Sure, but where? In lib/* somewhere? I''ll need it to get loaded before > any of these models get loaded. (Or I would have to add a ''require'' to > each commentable model.)You have a number of choices: 1. /lib/commentable.rb module Commentable def self.included(base) base.has_many :subscriptions, :as => :subscribable # and so on end end /app/models/blog_post.rb class BlogPost < AR::B include Commentable # rest of class definition end 2. /lib/commentable.rb # as in 1, but after the end of the module (or in environment.rb): class ActiveRecord::Base def self.acts_as_commentable include Commentable end end /app/models/blog_post.rb class BlogPost < AR::B acts_as_commentable end 3 (probably not recommended). /config/environment.rb class ActiveRecord::Base def self.acts_as_commentable has_many :subscriptions, ;as => :subscribable # and the other has_manys end end 4. Write an acts_as plugin (but call it something else -- I think acts_as_commentable is already taken as a plugin name). Does that help? Best, -- Marnen Laibow-Koser http://www.marnen.org marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org -- Posted via http://www.ruby-forum.com/.
Many thanks... #2 is what I was thinking, but I don''t understand how lib/commentable.rb would get loaded in that case? On Oct 23, 1:12 pm, Marnen Laibow-Koser <rails-mailing-l...@andreas- s.net> wrote:> Scott Johnson wrote: > > On Oct 23, 11:11 am, Marnen Laibow-Koser <rails-mailing-l...@andreas- > > s.net> wrote: > >> Define it as an ActiveRecord::Base class method. > > > Sure, but where? In lib/* somewhere? I''ll need it to get loaded before > > any of these models get loaded. (Or I would have to add a ''require'' to > > each commentable model.) > > You have a number of choices: > > 1. > /lib/commentable.rb > module Commentable > def self.included(base) > base.has_many :subscriptions, :as => :subscribable > # and so on > end > end > > /app/models/blog_post.rb > class BlogPost < AR::B > include Commentable > > # rest of class definition > end > > 2. > /lib/commentable.rb > # as in 1, but after the end of the module (or in environment.rb): > class ActiveRecord::Base > def self.acts_as_commentable > include Commentable > end > end > > /app/models/blog_post.rb > class BlogPost < AR::B > acts_as_commentable > end > > 3 (probably not recommended). > /config/environment.rb > class ActiveRecord::Base > def self.acts_as_commentable > has_many :subscriptions, ;as => :subscribable > # and the other has_manys > end > end > > 4. Write an acts_as plugin (but call it something else -- I think > acts_as_commentable is already taken as a plugin name). > > Does that help? > > Best, > -- > Marnen Laibow-Koserhttp://www.marnen.org > mar...-sbuyVjPbboAdnm+yROfE0A@public.gmane.org > -- > Posted viahttp://www.ruby-forum.com/.
Scott Johnson wrote:> Many thanks... #2 is what I was thinking, but I don''t understand how > lib/commentable.rb would get loaded in that case? > > > On Oct 23, 1:12 pm, Marnen Laibow-Koser <rails-mailing-l...@andreas-Ah, good point -- I''ve never done it that way, so I didn''t think of that. Rails'' autoloading might take care of it, but in development mode maybe not. I''ll have to check. Best, -- Marnen Laibow-Koser http://www.marnen.org marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org -- Posted via http://www.ruby-forum.com/.
In most projects I''m using an initializer to load all lib/*.rb files,
like:
config/initializers/requires.rb:
# auto-load all ruby files from RAILS_ROOT/lib/
Dir[File.join(RAILS_ROOT, ''lib'',
''*.rb'')].each do |file|
require file
Note, if you have any files you do not want auto-loaded, you certainly
don''t want to use that initializer :). Alternate option would be to
create a very simple plugin:
vender/plugins/acts_as_commentable/init.rb:
class ActiveRecord::Base
def self.acts_as_commentable
include Commentable
end
end
This should work as well.
- lukas
On Oct 23, 11:33 pm, Scott Johnson
<sc...-wIW8SF+lElu2kH9Ulgv/9g@public.gmane.org>
wrote:> Many thanks... #2 is what I was thinking, but I don''t understand
how
> lib/commentable.rb would get loaded in that case?
>
> On Oct 23, 1:12 pm, Marnen Laibow-Koser <rails-mailing-l...@andreas-
>
> s.net> wrote:
> > Scott Johnson wrote:
> > > On Oct 23, 11:11 am, Marnen Laibow-Koser
<rails-mailing-l...@andreas-
> > > s.net> wrote:
> > >> Define it as an ActiveRecord::Base class method.
>
> > > Sure, but where? In lib/* somewhere? I''ll need it to get
loaded before
> > > any of these models get loaded. (Or I would have to add a
''require'' to
> > > each commentable model.)
>
> > You have a number of choices:
>
> > 1.
> > /lib/commentable.rb
> > module Commentable
> > def self.included(base)
> > base.has_many :subscriptions, :as => :subscribable
> > # and so on
> > end
> > end
>
> > /app/models/blog_post.rb
> > class BlogPost < AR::B
> > include Commentable
>
> > # rest of class definition
> > end
>
> > 2.
> > /lib/commentable.rb
> > # as in 1, but after the end of the module (or in environment.rb):
> > class ActiveRecord::Base
> > def self.acts_as_commentable
> > include Commentable
> > end
> > end
>
> > /app/models/blog_post.rb
> > class BlogPost < AR::B
> > acts_as_commentable
> > end
>
> > 3 (probably not recommended).
> > /config/environment.rb
> > class ActiveRecord::Base
> > def self.acts_as_commentable
> > has_many :subscriptions, ;as => :subscribable
> > # and the other has_manys
> > end
> > end
>
> > 4. Write an acts_as plugin (but call it something else -- I think
> > acts_as_commentable is already taken as a plugin name).
>
> > Does that help?
>
> > Best,
> > --
> > Marnen Laibow-Koserhttp://www.marnen.org
> > mar...-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
> > --
> > Posted viahttp://www.ruby-forum.com/.
>
>