1. A category has parent categories. 2. A product is in many categories and a category has many products. 3. Products and category both have images in the same image table. ie. a product and / or category could have multiple images.<=== my question is related to this So among other things I presume I have to do the following: class Category < ActiveRecord:Base #... has_and_belongs_to_many products acts_as_tree :order => "name" #... end class Product < ActiveRecord:Base #... has_and_belongs_to_many categories #... end class Image < ActiveRecord:Base #... # ?? #... end Lets say the image table sql looks like this: create table images ( image_id int not null, entity_id int not null, entity_type varchar(20) not null, image_path varchar(255) not null, image_type varchar(20) not null, primary key(image_id) ); For example if i were to store the "BIG", "SMALL" images for a category in the above table, I would do: insert into images values(1, 1, "CATEGORY", "/big/smile1.jpg", "BIG"); insert into images values(1, 1, "CATEGORY", "/small/smile2.jpg", "SMALL"); Also, for example if I were to store the "SMALL", "MEDIUM" images for a product in the above same table, I would do: insert into images values(1, 1, "PRODUCT", "/big/hifi1.jpg", "SMALL"); insert into images values(1, 1, "PRODUCT", "/small/hifi2.jpg", "MEDIUM"); My question is how do I tell my app using ActiveRecord to map the one to many association between category and images AND between product and images in the above scenario where the product and category images map to the same table? Example code would be a great help. Thanks. -- Posted via http://www.ruby-forum.com/.
> My question is how do I tell my app using ActiveRecord to map the one to > many association between category and images AND between product and > images in the above scenario where the product and category images map > to the same table? Example code would be a great help.If I were in your shoes, I would just put two foreign keys in the image table, one for categories and one for products. Then, images would have: belongs_to :product belongs_to :category And then, products and categories would both have: has_many :images Sure, you''ll be wasting a field in every image record. Big deal. You can have this running in like five minutes, and it''ll work very easily. -- Posted via http://www.ruby-forum.com/.
You could also use a polymorphic association. On Sunday, April 23, 2006, at 4:13 AM, Bryan Duxbury wrote:> >> My question is how do I tell my app using ActiveRecord to map the one to >> many association between category and images AND between product and >> images in the above scenario where the product and category images map >> to the same table? Example code would be a great help. > >If I were in your shoes, I would just put two foreign keys in the image >table, one for categories and one for products. Then, images would have: > >belongs_to :product >belongs_to :category > >And then, products and categories would both have: > >has_many :images > >Sure, you''ll be wasting a field in every image record. Big deal. You can >have this running in like five minutes, and it''ll work very easily. > >-- >Posted via http://www.ruby-forum.com/. >_______________________________________________ >Rails mailing list >Rails@lists.rubyonrails.org >http://lists.rubyonrails.org/mailman/listinfo/rails_Kevin -- Posted with http://DevLists.com. Sign up and save your mailbox.
I might be misunderstanding your problem here, but thought I''d offer my advice just in case it''s applicable.. The other day I was trying to do something similar.. I had a User model, and wanted the user to be able to select a list of genres of music that they listen to. I also wanted to allow them to pick genres that they as a band play (if they were in fact in a band). So I''d need two join tables, one that maps users to personal_genres and one that maps users to band_genres. The problem is, I wanted to have only a single genre lookup table, that both band_genres and personal_genres relate to. The way I solved it was this: in User.rb: has_and_belongs_to_many :personal_genres, :class_name => "Genre", :join_table => "personal_genres_scouts" has_and_belongs_to_many :band_genres, :class_name => ''Genre'', :join_table => "band_genres_scouts" and of course I had the following tables: mysql> select * from genres limit 5; +----+------------+--------------------+ | id | short_name | genre_name | +----+------------+--------------------+ | 1 | AD | Adult/Contemporary | | 2 | BL | Blues | | 3 | CO | Country | | 4 | DA | Dance/Electronica | | 5 | EMO | EMO | +----+------------+--------------------+ mysql> select * from band_genres_users limit 5; +----------+----------+ | user_id | genre_id | +----------+----------+ | 709 | 10 | | 709 | 13 | | 709 | 14 | | 716 | 8 | | 716 | 13 | +----------+----------+ mysql> select * from personal_genres_users limit 5; +----------+----------+ | user_id | genre_id | +----------+----------+ | 708 | 2 | | 708 | 6 | | 708 | 15 | | 708 | 8 | | 708 | 12 | +----------+----------+ so perhaps you could do something similar, by having both products and images mapped to a single table, by specifying the join table and the class name in your model. Mike On 23 Apr 2006 02:15:43 -0000, Kevin Olbrich < devlists-rubyonrails@devlists.com> wrote:> > You could also use a polymorphic association. > > On Sunday, April 23, 2006, at 4:13 AM, Bryan Duxbury wrote: > > > >> My question is how do I tell my app using ActiveRecord to map the one > to > >> many association between category and images AND between product and > >> images in the above scenario where the product and category images map > >> to the same table? Example code would be a great help. > > > >If I were in your shoes, I would just put two foreign keys in the image > >table, one for categories and one for products. Then, images would have: > > > >belongs_to :product > >belongs_to :category > > > >And then, products and categories would both have: > > > >has_many :images > > > >Sure, you''ll be wasting a field in every image record. Big deal. You can > >have this running in like five minutes, and it''ll work very easily. > > > >-- > >Posted via http://www.ruby-forum.com/. > >_______________________________________________ > >Rails mailing list > >Rails@lists.rubyonrails.org > >http://lists.rubyonrails.org/mailman/listinfo/rails > > > _Kevin > > -- > Posted with http://DevLists.com. Sign up and save your mailbox. > _______________________________________________ > Rails mailing list > Rails@lists.rubyonrails.org > http://lists.rubyonrails.org/mailman/listinfo/rails >-------------- next part -------------- An HTML attachment was scrubbed... URL: http://wrath.rubyonrails.org/pipermail/rails/attachments/20060423/4e2e9266/attachment.html
Hi, Mike, the solution you presented works and the approach you present has definitely crossed my mind. In this approach one can get the functionality of a one to many association by actually turning it into a many to one and a one to many association using the join table. I come from the hibernate world of doing things where you would be able to do this one to many association without turning it into a many to one and one to many association. In my case a product could have many images and so could a category could have many images. An image on the other hand belongs ONLY TO ONE category or ONLY TO ONE product. If I follow your approach, the one down side to it is that I will loose this semantic at the database level i.e the image belongs to only one product or a category. Though at the business logic level I know that I am just using the many to many mapping as a means of doing my one to many association. Thank you. Mike Garey wrote:> I might be misunderstanding your problem here, but thought I''d offer my > advice just in case it''s applicable.. The other day I was trying to do > something similar.. I had a User model, and wanted the user to be able > to > select a list of genres of music that they listen to. I also wanted to > allow them to pick genres that they as a band play (if they were in fact > in > a band). So I''d need two join tables, one that maps users to > personal_genres and one that maps users to band_genres. The problem is, > I > wanted to have only a single genre lookup table, that both band_genres > and > personal_genres relate to. The way I solved it was this: > > in User.rb: > > has_and_belongs_to_many :personal_genres, :class_name => "Genre", > :join_table => "personal_genres_scouts" > has_and_belongs_to_many :band_genres, :class_name => ''Genre'', > :join_table > => "band_genres_scouts" > > > and of course I had the following tables: > > mysql> select * from genres limit 5; > +----+------------+--------------------+ > | id | short_name | genre_name | > +----+------------+--------------------+ > | 1 | AD | Adult/Contemporary | > | 2 | BL | Blues | > | 3 | CO | Country | > | 4 | DA | Dance/Electronica | > | 5 | EMO | EMO | > +----+------------+--------------------+ > > mysql> select * from band_genres_users limit 5; > +----------+----------+ > | user_id | genre_id | > +----------+----------+ > | 709 | 10 | > | 709 | 13 | > | 709 | 14 | > | 716 | 8 | > | 716 | 13 | > +----------+----------+ > > mysql> select * from personal_genres_users limit 5; > +----------+----------+ > | user_id | genre_id | > +----------+----------+ > | 708 | 2 | > | 708 | 6 | > | 708 | 15 | > | 708 | 8 | > | 708 | 12 | > +----------+----------+ > > so perhaps you could do something similar, by having both products and > images mapped to a single table, by specifying the join table and the > class > name in your model. > > Mike > > > On 23 Apr 2006 02:15:43 -0000, Kevin Olbrich <-- Posted via http://www.ruby-forum.com/.
Category has_many :images, :as=>:attachable Product has_many :images, :as=>:attachable Image belongs_to :attachable, :polymorphic=>true The image table should have a attachable_type varchar(255) attachable_id integer you can then call category.images product.images I don''t know if polymorphic associations work with has_one, if not, just make sure you set it up with an appropriate limit to get just the most recent one. On Sunday, April 23, 2006, at 6:22 AM, Mufaddal Khumri wrote:>Hi, > >Mike, the solution you presented works and the approach you present has >definitely crossed my mind. In this approach one can get the >functionality of a one to many association by actually turning it into a >many to one and a one to many association using the join table. I come >from the hibernate world of doing things where you would be able to do >this one to many association without turning it into a many to one and >one to many association. > >In my case a product could have many images and so could a category >could have many images. An image on the other hand belongs ONLY TO ONE >category or ONLY TO ONE product. If I follow your approach, the one down >side to it is that I will loose this semantic at the database level i.e >the image belongs to only one product or a category. Though at the >business logic level I know that I am just using the many to many >mapping as a means of doing my one to many association. > >Thank you. > >Mike Garey wrote: >> I might be misunderstanding your problem here, but thought I''d offer my >> advice just in case it''s applicable.. The other day I was trying to do >> something similar.. I had a User model, and wanted the user to be able >> to >> select a list of genres of music that they listen to. I also wanted to >> allow them to pick genres that they as a band play (if they were in fact >> in >> a band). So I''d need two join tables, one that maps users to >> personal_genres and one that maps users to band_genres. The problem is, >> I >> wanted to have only a single genre lookup table, that both band_genres >> and >> personal_genres relate to. The way I solved it was this: >> >> in User.rb: >> >> has_and_belongs_to_many :personal_genres, :class_name => "Genre", >> :join_table => "personal_genres_scouts" >> has_and_belongs_to_many :band_genres, :class_name => ''Genre'', >> :join_table >> => "band_genres_scouts" >> >> >> and of course I had the following tables: >> >> mysql> select * from genres limit 5; >> +----+------------+--------------------+ >> | id | short_name | genre_name | >> +----+------------+--------------------+ >> | 1 | AD | Adult/Contemporary | >> | 2 | BL | Blues | >> | 3 | CO | Country | >> | 4 | DA | Dance/Electronica | >> | 5 | EMO | EMO | >> +----+------------+--------------------+ >> >> mysql> select * from band_genres_users limit 5; >> +----------+----------+ >> | user_id | genre_id | >> +----------+----------+ >> | 709 | 10 | >> | 709 | 13 | >> | 709 | 14 | >> | 716 | 8 | >> | 716 | 13 | >> +----------+----------+ >> >> mysql> select * from personal_genres_users limit 5; >> +----------+----------+ >> | user_id | genre_id | >> +----------+----------+ >> | 708 | 2 | >> | 708 | 6 | >> | 708 | 15 | >> | 708 | 8 | >> | 708 | 12 | >> +----------+----------+ >> >> so perhaps you could do something similar, by having both products and >> images mapped to a single table, by specifying the join table and the >> class >> name in your model. >> >> Mike >> >> >> On 23 Apr 2006 02:15:43 -0000, Kevin Olbrich < > > >-- >Posted via http://www.ruby-forum.com/. >_______________________________________________ >Rails mailing list >Rails@lists.rubyonrails.org >http://lists.rubyonrails.org/mailman/listinfo/rails_Kevin -- Posted with http://DevLists.com. Sign up and save your mailbox.
Kevin, I will give this approach a try. Thank you for the input on this. Regards. Kevin Olbrich wrote:> Category > has_many :images, :as=>:attachable > > Product > has_many :images, :as=>:attachable > > Image > belongs_to :attachable, :polymorphic=>true > > The image table should have a > attachable_type varchar(255) > attachable_id integer > > you can then call > > category.images > product.images > > I don''t know if polymorphic associations work with has_one, if not, just > make sure you set it up with an appropriate limit to get just the most > recent one. > > _Kevin-- Posted via http://www.ruby-forum.com/.
I finally got sometime this morning to write an example class to
exercise the polymorphic feature. I get the following exception:
/usr/lib/ruby/gems/1.8/gems/activesupport-1.2.5/lib/active_support/core_ext/hash/keys.rb:48:in
`assert_valid_keys'': Unknown key(s): as (ArgumentError)
from
/usr/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/associations.rb:343:in
`has_many_without_reflection''
from (eval):5:in `has_many''
from db.rb:8
Am I using the wrong version of activerecord or something?
These are the versions I am using:
ruby 1.8.3 (2005-06-23) [i486-linux]
activerecord (1.13.2)
##################################
Here is the example class I wrote:
##################################
require "rubygems"
require_gem "activerecord"
ActiveRecord::Base.establish_connection(:adapter => "mysql", :host
=>
"localhost", :database => "myTestDb")
class Stock < ActiveRecord::Base
has_many :trades
has_many :notes, :as => :attachable
end
class Trade < ActiveRecord::Base
belongs_to :stock
has_many :notes, :as => :attachable
end
class Note < ActiveRecord::Base
belongs_to :attachable, :polymorphic => true
end
stock = Stock.new
stock.ticker = "GTT"
stock.company = "Giraffee Co."
note = Note.new
note.text="Hello"
stock.notes << note
stock.save;
##############################
Here is the corresponding sql:
##############################
CREATE TABLE `notes` (
`id` int(11) NOT NULL auto_increment,
`attachable_type` varchar(255) NOT NULL default '''',
`attachable_id` int(11) NOT NULL default ''0'',
`text` text,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
CREATE TABLE `stocks` (
`id` int(11) NOT NULL auto_increment,
`company` varchar(255) NOT NULL default '''',
`ticker` varchar(8) NOT NULL default '''',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
CREATE TABLE `trades` (
`id` int(11) NOT NULL auto_increment,
`stock_id` int(11) NOT NULL default ''0'',
`qty` int(11) NOT NULL default ''0'',
`price` decimal(10,2) NOT NULL default ''0.00'',
`commission` decimal(10,2) NOT NULL default ''0.00'',
`traded_on` datetime NOT NULL default ''0000-00-00 00:00:00'',
`bs_flag` varchar(4) NOT NULL default '''',
PRIMARY KEY (`id`),
KEY `fk_trades_stock` (`stock_id`),
CONSTRAINT `fk_trades_stock` FOREIGN KEY (`stock_id`) REFERENCES
`stocks` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
Mufaddal Khumri wrote:> Kevin,
>
> I will give this approach a try. Thank you for the input on this.
>
> Regards.
>
> Kevin Olbrich wrote:
>> Category
>> has_many :images, :as=>:attachable
>>
>> Product
>> has_many :images, :as=>:attachable
>>
>> Image
>> belongs_to :attachable, :polymorphic=>true
>>
>> The image table should have a
>> attachable_type varchar(255)
>> attachable_id integer
>>
>> you can then call
>>
>> category.images
>> product.images
>>
>> I don''t know if polymorphic associations work with has_one, if
not, just
>> make sure you set it up with an appropriate limit to get just the most
>> recent one.
>>
>> _Kevin
--
Posted via http://www.ruby-forum.com/.
Yeah, you are using an old version. Polymorphic associations require rails 1.1. Not sure which version of activerecord that corresponds with. You will probably need to upgrade your ruby too, I seem to recall that rails has issues with 1.8.3. On Sunday, April 23, 2006, at 9:24 PM, Mufaddal Khumri wrote:>I finally got sometime this morning to write an example class to >exercise the polymorphic feature. I get the following exception: > >/usr/lib/ruby/gems/1.8/gems/activesupport-1.2.5/lib/active_support/ >core_ext/hash/keys.rb:48:in >`assert_valid_keys'': Unknown key(s): as (ArgumentError) > from >/usr/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/ >associations.rb:343:in >`has_many_without_reflection'' > from (eval):5:in `has_many'' > from db.rb:8 > >Am I using the wrong version of activerecord or something? >These are the versions I am using: >ruby 1.8.3 (2005-06-23) [i486-linux] >activerecord (1.13.2) > >################################## >Here is the example class I wrote: >################################## > >require "rubygems" >require_gem "activerecord" > >ActiveRecord::Base.establish_connection(:adapter => "mysql", :host => >"localhost", :database => "myTestDb") > >class Stock < ActiveRecord::Base > has_many :trades > has_many :notes, :as => :attachable >end > >class Trade < ActiveRecord::Base > belongs_to :stock > has_many :notes, :as => :attachable >end > >class Note < ActiveRecord::Base > belongs_to :attachable, :polymorphic => true >end > >stock = Stock.new >stock.ticker = "GTT" >stock.company = "Giraffee Co." >note = Note.new >note.text="Hello" >stock.notes << note >stock.save; > >############################## >Here is the corresponding sql: >############################## > >CREATE TABLE `notes` ( > `id` int(11) NOT NULL auto_increment, > `attachable_type` varchar(255) NOT NULL default '''', > `attachable_id` int(11) NOT NULL default ''0'', > `text` text, > PRIMARY KEY (`id`) >) ENGINE=MyISAM DEFAULT CHARSET=latin1; > >CREATE TABLE `stocks` ( > `id` int(11) NOT NULL auto_increment, > `company` varchar(255) NOT NULL default '''', > `ticker` varchar(8) NOT NULL default '''', > PRIMARY KEY (`id`) >) ENGINE=InnoDB DEFAULT CHARSET=latin1; > >CREATE TABLE `trades` ( > `id` int(11) NOT NULL auto_increment, > `stock_id` int(11) NOT NULL default ''0'', > `qty` int(11) NOT NULL default ''0'', > `price` decimal(10,2) NOT NULL default ''0.00'', > `commission` decimal(10,2) NOT NULL default ''0.00'', > `traded_on` datetime NOT NULL default ''0000-00-00 00:00:00'', > `bs_flag` varchar(4) NOT NULL default '''', > PRIMARY KEY (`id`), > KEY `fk_trades_stock` (`stock_id`), > CONSTRAINT `fk_trades_stock` FOREIGN KEY (`stock_id`) REFERENCES >`stocks` (`id`) ON DELETE CASCADE >) ENGINE=InnoDB DEFAULT CHARSET=latin1; > >Mufaddal Khumri wrote: >> Kevin, >> >> I will give this approach a try. Thank you for the input on this. >> >> Regards. >> >> Kevin Olbrich wrote: >>> Category >>> has_many :images, :as=>:attachable >>> >>> Product >>> has_many :images, :as=>:attachable >>> >>> Image >>> belongs_to :attachable, :polymorphic=>true >>> >>> The image table should have a >>> attachable_type varchar(255) >>> attachable_id integer >>> >>> you can then call >>> >>> category.images >>> product.images >>> >>> I don''t know if polymorphic associations work with has_one, if not, just >>> make sure you set it up with an appropriate limit to get just the most >>> recent one. >>> >>> _Kevin > > >-- >Posted via http://www.ruby-forum.com/. >_______________________________________________ >Rails mailing list >Rails@lists.rubyonrails.org >http://lists.rubyonrails.org/mailman/listinfo/rails_Kevin -- Posted with http://DevLists.com. Sign up and save your mailbox.
Worked like a charm after the upgrade. Thanks. Kevin Olbrich wrote:> Yeah, you are using an old version. Polymorphic associations require > rails 1.1. > Not sure which version of activerecord that corresponds with. > > You will probably need to upgrade your ruby too, I seem to recall that > rails has issues with 1.8.3. > > On Sunday, April 23, 2006, at 9:24 PM, Mufaddal Khumri wrote: >> from (eval):5:in `has_many'' >> >> >>stock.ticker = "GTT" >>CREATE TABLE `notes` ( >> `ticker` varchar(8) NOT NULL default '''', >> `bs_flag` varchar(4) NOT NULL default '''', >>> >>>> belongs_to :attachable, :polymorphic=>true >>>> I don''t know if polymorphic associations work with has_one, if not, just >>Rails@lists.rubyonrails.org >>http://lists.rubyonrails.org/mailman/listinfo/rails > > > _Kevin-- Posted via http://www.ruby-forum.com/.