Ok, I have 2 very simple has_many :through associations I need to
create and, despite bashing my brain and my computer against this
problem repeatedly for 2 days, I cannot figure out what I am doing
wrong as I cannot get the has_many :through to work. I think I have
fundamentally misunderstood how to do has_many :throughs, so I am
going to ruby script/destroy the models I have created and try again.
I''m going to post here my steps to create these relationship, can
someone please let me know if I''m doing this correctly? First, the
relationships.
Contacts <== Account_Contacts ==> Account <== Account_Attachments
==>
Attachments
the 2 word tables are the join tables, basically Contacts and
Attachments have a many to many relationship with Account.
1. ruby script/generate model Account
2. ruby script/generate model Contact
3. ruby script/generate model Attachment
4. fill in migration file for the account table (no need to reference
a join table here)
5. fill in migration file for the contact table (here I am creating
the Account_Contacts table with integer fields for Account and
Contact, as well as a category field)
6. fill in migration file for the attachment table (Same as the
contact table, I create Account_Attachments here with the same
fields).
7. rake db:migrate
Ok, now I should have a functioning has_many :through relationship,
right? When I attempted to use this relationship in the console like
so:
acct = Account.find(1)
file = Attachment.find(1)
acct.attachments.create( :attachment => file, :category =>
"test")
I get the following error message:
NameError: uninitialized constant Account::AccountAttachment
from C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/
activesupport-1.4.2/lib
/active_support/dependencies.rb:477:in `const_missing''
from C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/
activerecord-1.15.3/lib
/active_record/base.rb:1360:in `compute_type''
from C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/
activerecord-1.15.3/lib
/active_record/reflection.rb:125:in `send''
from C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/
activerecord-1.15.3/lib
/active_record/reflection.rb:125:in `klass''
from C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/
activerecord-1.15.3/lib
/active_record/reflection.rb:177:in `source_reflection''
from C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/
activerecord-1.15.3/lib
/active_record/reflection.rb:177:in `collect''
from C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/
activerecord-1.15.3/lib
/active_record/reflection.rb:177:in `source_reflection''
from C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/
activerecord-1.15.3/lib
/active_record/reflection.rb:186:in `check_validity!''
from C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/
activerecord-1.15.3/lib
/active_record/associations/has_many_through_association.rb:6:in
`initialize''
from C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/
activerecord-1.15.3/lib
/active_record/associations.rb:934:in `new''
from C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/
activerecord-1.15.3/lib
/active_record/associations.rb:934:in `attachments''
from (irb):3
What did I do wrong here?
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On Dec 19, 2007, at 12:57 PM, JonathanB wrote:> > Ok, now I should have a functioning has_many :through relationship, > right? When I attempted to use this relationship in the console like > so: >You need to edit the models and add something like contacts.rb has_many :account_contacts has_many :accounts, :through => :account_contacts account.rb has_many :account_contacts has_many :contacts, :though => :account_contacts has_many :account_attachments has_many :attachments, :through => :account_attachments Peace, Phillip --~--~---------~--~----~------------~-------~--~----~ 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?hl=en -~----------~----~----~----~------~----~------~--~---
Phillip Koebbe wrote:> On Dec 19, 2007, at 12:57 PM, JonathanB wrote: > > contacts.rb > has_many :account_contacts > has_many :accounts, :through => :account_contacts > > account.rb > has_many :account_contacts > has_many :contacts, :though => :account_contacts > has_many :account_attachments > has_many :attachments, :through => :account_attachments > > Peace, > PhillipPhillip has a really NICE Short version. here is a longer version, if you are interested. ___________________________________________________ OLD WAY - has_and_belongs_to_many :my_model This is an out of date technique to set up the many-to-many table. A major limitation to this method is that you cannot have any more fields in the table then the 2 joining fields, and the join table does not use a primary field key called id. You cant sort joined fields very easily with this method. This technique is very easy to set up. The table name is the plural names of the 2 joining tables, in alphabetical order, separated by an underscore. Table C and B would be BS_CS. The only 2 fields in the join table would be b_id and c_id. NEW WAY - has_many :through This technique allows the join table to have as many fields as you want. You need a model, for the joining, to make this work. You can just generate a model. But if you need more fields, you can scaffold. The join table also gets the primary key field (id) that is automatically generated in most cases. The joining table can be named what ever you want. The current trend is to use a table name that just has one word, and usually ends in -ship, -tion, or -ment. There can be endless hours of debate over the name of the joining table. You will need to have the 2 joining tables foreign key fields in this table, like the fashion <tablename>_id, that are not pluralized. If you wanted to join table A and table B, an example of the joining table could be: TABLES A id (integer, primary key) name (string) B id (integer, primary key) name (string) AB (many table for joining tables A and B) id (integer, primary key) a_id (integer) b_id (integer) (more fields) The MODELS A has_many :ABs has_many :Bs :through => :ABs AB belongs_to :A belongs_to :B B has_many :ABs has_many :As :through => :ABs SOME OPTIONS has_many :mytable, :foreign_key => ''myfield_id'', :class_name => ''myclassname'', :dependent => :destroy -- 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@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On Dec 19, 2007, at 2:05 PM, gemblon (t.b.) wrote:> > Phillip has a really NICE Short version. > here is a longer version, if you are interested. > ___________________________________________________ >Not just longer ;), but actually correct. I forgot the join table models that have the :belongs_to. I don''t think it would have worked without that! Thanks gemblon! Peace, Phillip --~--~---------~--~----~------------~-------~--~----~ 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?hl=en -~----------~----~----~----~------~----~------~--~---