thr3ads.net - Rails - Help With has_many and belongs_to :through assocaitions [Oct 2006]

If this information is useful, please help other people find it:
Share via:

markdodwell-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org

2006-Oct-23 20:14 UTC

Help With has_many and belongs_to :through assocaitions

Hi all, I am having problems with some reasonably complex assocaitions
involving has_many and belongs_to with the :through option.

I have three models:

class Site < ActiveRecord::Base
  has_many :site_page_relationships
  has_many :pages, :through =>
:pagesite_page_relationships_relationships, :source => :child_page
end

class PageRelationship < ActiveRecord::Base
  belongs_to :site
  belongs_to :parent_page, :foreign_key => :parent_page_id,
        :class_name => :page
  belongs_to :child_page, :foreign_key => :child_page_id,
        :class_name => :page
end

class Page < ActiveRecord::Base
  has_many :page_relationships, :foreign_key => :child_page_id
  has_many :child_pages, :through => :page_relationships,
        :source => :child_page
  has_many :parent_pages, :through => :page_relationships,
        :source => :parent_page
end

The idea being that you can have multipe sites each with their own
sitetree, and the ability to share pages between sites but in different
positions in the site tree.

When I try the following in ''script/console'':
>> page1 = Page.new=> #<Page:0x279bb60 @attributes={},
@new_record=true>>> page1.save
=> true>> page2 = Page.new=> #<Page:0x27944b4 @attributes={},
@new_record=true>>> page2.save
=> true>> site = Site.new=> #<Site:0x278e208 @attributes={"name"=>nil,
"updated_at"=>nil,
"url"=>nil, "description"=>nil,
"created_at"=>nil}, @new_record=true>>> site.save
=> true>> rel1 = PageRelationship.new(:parent_page => page1, :child_page =>
page2, :site => site)TypeError: can''t convert Symbol into String
        from
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active_record/base.rb:1003:in
`type_name_with_module''
        from
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active_record/base.rb:1242:in
`compute_type''
        from
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active_record/reflection.rb:112:in
`klass''
        from
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active_record/associations/association_proxy.rb:133:in
`raise_on_type_mismatch''
        from
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active_record/associations/belongs_to_association.rb:22:in
`replace''
        from
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active_record/associations.rb:850:in
`child_page=''
        from
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active_record/base.rb:1510:in
`attributes=''
        from
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active_record/base.rb:1509:in
`attributes=''
        from
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active_record/base.rb:1354:in
`initialize_without_callbacks''
        from
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active_record/callbacks.rb:236:in
`initialize''
        from (irb):11
        from :0

You can see that I get this error? It''s really bugging me, I
can''t
figure out why. Any suggestions/ideas would be much appreciated.

Many Thanks

Mark Dodwell


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

Bala Paranj

2006-Oct-23 20:31 UTC

head link

Re: Help With has_many and belongs_to :through assocaitions

>
> class Site < ActiveRecord::Base
> has_many :site_page_relationships
> has_many :pages, :through =>
> :pagesite_page_relationships_relationships, :source => :child_page
> end
>
> class PageRelationship < ActiveRecord::Base
> belongs_to :site
> belongs_to :parent_page, :foreign_key => :parent_page_id,
>        :class_name => :page
> belongs_to :child_page, :foreign_key => :child_page_id,
>        :class_name => :page
> end
>
> class Page < ActiveRecord::Base
> has_many :page_relationships, :foreign_key => :child_page_id
> has_many :child_pages, :through => :page_relationships,
>        :source => :child_page
> has_many :parent_pages, :through => :page_relationships,
>        :source => :parent_page
> end
>
> The idea being that you can have multipe sites each with their own
> sitetree, and the ability to share pages between sites but in different
> positions in the site tree.


If I understood your domain, it is like :

Site 1 -----> SiteTree 1
Site 2 ------> SiteTree 2
and so on.

Then SiteTree has many Pages. So it looks like you have one-to-one
relationship between Site and SiteTree. SiteTree and Pages many to many
relationship.

If that is the case then your model should break the many-to-many
relationship between SiteTree and Page classes.


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

Josh Susser

2006-Oct-23 20:41 UTC

head link

Re: Help With has_many and belongs_to :through assocaitions

markdodwell-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org
wrote:> Hi all, I am having problems with some reasonably complex assocaitions
> involving has_many and belongs_to with the :through option.
> 
> I have three models:
> 
> class Site < ActiveRecord::Base
>   has_many :site_page_relationships
>   has_many :pages, :through =>
> :pagesite_page_relationships_relationships, :source => :child_page
> end
> 
> class PageRelationship < ActiveRecord::Base
>   belongs_to :site
>   belongs_to :parent_page, :foreign_key => :parent_page_id,
>         :class_name => :page
>   belongs_to :child_page, :foreign_key => :child_page_id,
>         :class_name => :page
> end
> 
> class Page < ActiveRecord::Base
>   has_many :page_relationships, :foreign_key => :child_page_id
>   has_many :child_pages, :through => :page_relationships,
>         :source => :child_page
>   has_many :parent_pages, :through => :page_relationships,
>         :source => :parent_page
> end
> 
> The idea being that you can have multipe sites each with their own
> sitetree, and the ability to share pages between sites but in different
> positions in the site tree.
> 
> When I try the following in ''script/console'':
> 
>>> page1 = Page.new
> => #<Page:0x279bb60 @attributes={}, @new_record=true>
>>> page1.save
> => true
>>> page2 = Page.new
> => #<Page:0x27944b4 @attributes={}, @new_record=true>
>>> page2.save
> => true
>>> site = Site.new
> => #<Site:0x278e208 @attributes={"name"=>nil,
"updated_at"=>nil,
> "url"=>nil, "description"=>nil,
"created_at"=>nil}, @new_record=true>
>>> site.save
> => true
>>> rel1 = PageRelationship.new(:parent_page => page1, :child_page
=> page2, :site => site)
> TypeError: can''t convert Symbol into String
>         from
>
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active_record/base.rb:1003:in
> `type_name_with_module''
Your Page model doesn''t have the right associations for a 
self-referential hmt relationship. You need two different has_many 
assocs for the parent and child refs to the join model. This is like 
having different aliases for your joins in SQL. Take a look at my 
posting on this:

http://blog.hasmanythrough.com/articles/2006/04/21/self-referential-through

Also, your Site class has some weird named assocs. That might be the 
source of your error. Remember, if the model name can''t be inferred
from
the assoc name, you need to specify it with options.

--
Josh Susser
http://blog.hasmanythrough.com


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

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

Bala Paranj

2006-Oct-23 21:02 UTC

head link

Re: Help With has_many and belongs_to :through assocaitions

>
>
> Your Page model doesn''t have the right associations for a
> self-referential hmt relationship. You need two different has_many
> assocs for the parent and child refs to the join model. This is like
> having different aliases for your joins in SQL. Take a look at my
> posting on this:
>
>
> http://blog.hasmanythrough.com/articles/2006/04/21/self-referential-through
>
> Also, your Site class has some weird named assocs. That might be the
> source of your error. Remember, if the model name can''t be
inferred from
> the assoc name, you need to specify it with options.

Edge  (n) <------------------->(1) Node -----
                                              ^_____|

Is the diagram correct? Node has the self-reference and you have one to many
relationship between the Node and the Edges.


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

Josh Susser

2006-Oct-23 21:40 UTC

head link

Re: Help With has_many and belongs_to :through assocaitions

Bala Paranj wrote:>>
>> Also, your Site class has some weird named assocs. That might be the
>> source of your error. Remember, if the model name can''t be
inferred from
>> the assoc name, you need to specify it with options.
> 
> 
> Edge  (n) <------------------->(1) Node -----
>                                               ^_____|
> 
> Is the diagram correct? Node has the self-reference and you have one to 
> many
> relationship between the Node and the Edges.
Yes.

--
Josh Susser
http://blog.hasmanythrough.com

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

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

markdodwell-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org

2006-Oct-23 23:33 UTC

head link

Re: Help With has_many and belongs_to :through assocaitions

Many thanks for all your help, I have now managed to fix it. After
reading John''s post '' Self-referential has_many :through
associations''
I sorted it.

Great to get such a quick response from people. First time I posted a
question here! Was very happy indeed. My new models which work are as
follows:

class Site < ActiveRecord::Base
  has_and_belongs_to_many :users
  has_many :page_relationships
  has_many :pages, :through => :page_relationships, :source =>
:child_page
end

class PageRelationship < ActiveRecord::Base
  belongs_to :site
  belongs_to :parent_page, :foreign_key =>
''parent_page_id'',
        :class_name => ''Page''
  belongs_to :child_page, :foreign_key => ''child_page_id'',
        :class_name => ''Page''
end

class Page < ActiveRecord::Base
  has_many :page_relationships_as_child, :foreign_key =>
''child_page_id'',
        :class_name => ''PageRelationship''
  has_many :page_relationships_as_parent, :foreign_key =>
''parent_page_id'',
        :class_name => ''PageRelationship''
  has_many :child_pages, :through => :page_relationships_as_child
  has_many :parent_pages, :through => :page_relationships_as_parent
end

Cheers again, Mark


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

Rails - Oct 2006 - Help With has_many and belongs_to :through assocaitions

Help With has_many and belongs_to :through assocaitions

Re: Help With has_many and belongs_to :through assocaitions

Re: Help With has_many and belongs_to :through assocaitions

Re: Help With has_many and belongs_to :through assocaitions

Re: Help With has_many and belongs_to :through assocaitions

Re: Help With has_many and belongs_to :through assocaitions