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Sudara

2006-May-18 14:35 UTC

[Rails] Model Madness: habtm vs through

This has me scratching my head:

a Person has many Things
a Person has many Collections
a Collection has many Things
  ...Things in a Collection are ordered
  ...Things in a Collection can be related to (created by) any User
  ...a collection has additional attributes, such as a name etc


I am confused about habtm in rails (especially when using 
acts_as_habtm_list) vs. going the :through route. Please tell me I am 
thinking too hard!

My current take:
-*-*-*-*-*-*-*-*
class Person < ActiveRecord::Base
    has_many :things
    has_many :collections
end

class Thing < ActiveRecord::Base
    belongs_to :person
    has_and_belongs_to_many :collections, :order =>
''position''
end

class Collection < ActiveRecord::Base
    belongs_to :person
    has_and_belongs_to_many :thing_collections, :order =>
''position''
end

class ThingCollection < ActiveRecord::Base
   has_and_belongs_to_many :collections
   has_and_belongs_to_many :things
   acts_as_list :scope => :collections
end
-*-*-*-*-*-*-*-*

Is that right?
or is it better to do something like this:

-*-*-*-*-*-
class Person < ActiveRecord::Base
    has_many :things
    has_many :collections
end

class Thing < ActiveRecord::Base
    belongs_to :person
    belongs_to :collection
    has_many :collections, :through => :thing_collections, :order => 
"position"
end

class Collection < ActiveRecord::Base
    belongs_to :person
    has_many :things, :through => :thing_collections, :order => 
"position"
end

class ThingCollection < ActiveRecord::Base
   belongs_to :collections
   belongs_to :things
   acts_as_list :scope => :collection_id
end
-*-*-*-*-*-*

Yes, I am in over my head.
Yes, I am smart, and willing to learn.
Yes, I want to built something that will last and be flexible...
No, I haven''t even moved on past the model, because I wish to 
understand...

Thanks!
sudara

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

Brian Chamberlain

2006-May-18 15:08 UTC

head link

[Rails] Model Madness: habtm vs through

Sudara,
I think you''re thinking too hard. From what you described I
don''t think you
need such a complicated data model.

What is the purpose of ThingCollection? Isn''t Collection a collection
of
things?

Have you read this?

http://blog.hasmanythrough.com/articles/2006/04/20/many-to-many-dance-off

-Brian




On 5/18/06, Sudara <rails@modernthings.net> wrote:>
> This has me scratching my head:
>
> a Person has many Things
> a Person has many Collections
> a Collection has many Things
>   ...Things in a Collection are ordered
>   ...Things in a Collection can be related to (created by) any User
>   ...a collection has additional attributes, such as a name etc
>
>
> I am confused about habtm in rails (especially when using
> acts_as_habtm_list) vs. going the :through route. Please tell me I am
> thinking too hard!
>
> My current take:
> -*-*-*-*-*-*-*-*
> class Person < ActiveRecord::Base
>     has_many :things
>     has_many :collections
> end
>
> class Thing < ActiveRecord::Base
>     belongs_to :person
>     has_and_belongs_to_many :collections, :order =>
''position''
> end
>
> class Collection < ActiveRecord::Base
>     belongs_to :person
>     has_and_belongs_to_many :thing_collections, :order =>
''position''
> end
>
> class ThingCollection < ActiveRecord::Base
>    has_and_belongs_to_many :collections
>    has_and_belongs_to_many :things
>    acts_as_list :scope => :collections
> end
> -*-*-*-*-*-*-*-*
>
> Is that right?
> or is it better to do something like this:
>
> -*-*-*-*-*-
> class Person < ActiveRecord::Base
>     has_many :things
>     has_many :collections
> end
>
> class Thing < ActiveRecord::Base
>     belongs_to :person
>     belongs_to :collection
>     has_many :collections, :through => :thing_collections, :order =>
> "position"
> end
>
> class Collection < ActiveRecord::Base
>     belongs_to :person
>     has_many :things, :through => :thing_collections, :order =>
> "position"
> end
>
> class ThingCollection < ActiveRecord::Base
>    belongs_to :collections
>    belongs_to :things
>    acts_as_list :scope => :collection_id
> end
> -*-*-*-*-*-*
>
> Yes, I am in over my head.
> Yes, I am smart, and willing to learn.
> Yes, I want to built something that will last and be flexible...
> No, I haven''t even moved on past the model, because I wish to
> understand...
>
> Thanks!
> sudara
>
> --
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
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njmacinnes@gmail.com

2006-May-18 15:20 UTC

head link

[Rails] Model Madness: habtm vs through

The only reason for using habtm instead of :through is it''s
simplicity. You don''t need to create a model class for the join table.
If you use habtm, the table would be called collections_things (the
two tables in alphabetical order). Just using a simple habtm wouldn''t
be enough for your purposes though, because you need it to be a list.
Now, I don''''t know about acts_as_habtm_list (by the name, it
sounds
like it might be quite useful for you), but I would do that using
:through. Replace all your habtms with has_many... :through =>
ThingCollection, and you''re set.
Hope all that made sense.
-Nathan

On 18/05/06, Sudara <rails@modernthings.net>
wrote:> This has me scratching my head:
>
> a Person has many Things
> a Person has many Collections
> a Collection has many Things
>   ...Things in a Collection are ordered
>   ...Things in a Collection can be related to (created by) any User
>   ...a collection has additional attributes, such as a name etc
>
>
> I am confused about habtm in rails (especially when using
> acts_as_habtm_list) vs. going the :through route. Please tell me I am
> thinking too hard!
>
> My current take:
> -*-*-*-*-*-*-*-*
> class Person < ActiveRecord::Base
>     has_many :things
>     has_many :collections
> end
>
> class Thing < ActiveRecord::Base
>     belongs_to :person
>     has_and_belongs_to_many :collections, :order =>
''position''
> end
>
> class Collection < ActiveRecord::Base
>     belongs_to :person
>     has_and_belongs_to_many :thing_collections, :order =>
''position''
> end
>
> class ThingCollection < ActiveRecord::Base
>    has_and_belongs_to_many :collections
>    has_and_belongs_to_many :things
>    acts_as_list :scope => :collections
> end
> -*-*-*-*-*-*-*-*
>
> Is that right?
> or is it better to do something like this:
>
> -*-*-*-*-*-
> class Person < ActiveRecord::Base
>     has_many :things
>     has_many :collections
> end
>
> class Thing < ActiveRecord::Base
>     belongs_to :person
>     belongs_to :collection
>     has_many :collections, :through => :thing_collections, :order =>
> "position"
> end
>
> class Collection < ActiveRecord::Base
>     belongs_to :person
>     has_many :things, :through => :thing_collections, :order =>
> "position"
> end
>
> class ThingCollection < ActiveRecord::Base
>    belongs_to :collections
>    belongs_to :things
>    acts_as_list :scope => :collection_id
> end
> -*-*-*-*-*-*
>
> Yes, I am in over my head.
> Yes, I am smart, and willing to learn.
> Yes, I want to built something that will last and be flexible...
> No, I haven''t even moved on past the model, because I wish to
> understand...
>
> Thanks!
> sudara
>
> --
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>

Sudara

2006-May-20 17:10 UTC

head link

[Rails] Re: Model Madness: habtm vs through

Thanks guys:

Brian:
As far as I know, *some* extra join model must exist if I want to employ 
lists. You are right, Collection is a collection of Things. But I would 
like to take advantage of the ordering built in with acts_as_list or 
acts_as_hatbm_list, and so my impression is that I need a table with a 
position column and tell it to acts_as_list

That link is great - that is where I came from. Part of it was 
informative, part of it was over my head and confusing.

Nathan:
Thanks for the confirmation...I believe what you suggested is working|

So, this is what I have:

-*-*-*-*-
class Thing < ActiveRecord::Base
    belongs_to :person
    has_many :collections, :through => :thing_collection, :order => 
"position"
end

class Collection < ActiveRecord::Base
    belongs_to :person
    has_many :things, :through => :thing_collection, :order => 
"position"
end

class ThingCollection < ActiveRecord::Base
   belongs_to :collection
   belongs_to :thing
   acts_as_list :scope => :collection, :order => :position
end

-*-*-*-*-

As far as I understand it, I can use acts_as_list here, specifying that 
I want to access ThingCollection via Collections as the scope.

When I start to move into the controllers, I am not quite clear what the 
easiest way to access my variables are...but, then again I still have 
some basic things to learn.

For example, I am doing this ugly thing in my Collections controller, in 
order to make the items in the collection availble for sorting.  I 
*know* there is an easier way.

def order
    @items = ThingCollection.find(:all, :conditions => [ 
"collection_id=", params[:id]])
end

Thanks,
sudara

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

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