similar to: has_one through belongs_to

Hi All, Probably this has been asked numerous times, I apologize already! Can somebody point me to a good tutorial on how Rails works with relations? I know about database design and normalization, I also know about programming in general (and OOP for that matter). Only thing I can say is that I''m following the "Four days on Rails" tutorial by John McCreesh. He writes

I''m having a difficult time wrapping my head around a set of models and their associations and seeing how they map into Rails. I''ll try to lay out my problem using the has_many and belongs_to structures. I have a RuleSpace, a Rule, and a Subject. A RuleSpace has_many Rules A RulesSpace has_many Subjects through Rules A Rule belongs_to (many) RuleSpaces A Rule has_many

Hi, I am very confused about an aspect of has_one and has_many relations, with regard to using the build method, and saving the belongs_to side. It''s a somewhat long post. so please bear with me :) First let''s consider the has_one scenario. Let''s say I have a student who must own exactly one car: class Student has_one(:car) end class Car belongs_to(:student)

Heya everyone! I am quite new to Rails and I am reading AWDwR. I am at Task E "Check Out!". I understand it quite well, but I have a problem with the last playground exercise: Add a Table which contains the payment types. All goes well, but I am not sure whether I should use has_many or has_one(as in the Playground wiki at http://wiki.pragprog.com/cgi-bin/wiki.cgi/PT-E-3). I use the

Here is my simple example... require ''rubygems'' require ''active_record'' ActiveRecord::Base.establish_connection :adapter => "sqlite3", :database => "has_many_through.db" ActiveRecord::Schema.define do create_table "containers", :force => true do |t| t.column :name, :string end create_table "shapes",

Hi, I''m trying to write a blog application where each post has a single header image associated. My models: ---------- class Post < ActiveRecord::Base belongs_to :blog has_many :images has_one :header end class Header < ActiveRecord::Base file_column :image_path end class Image < ActiveRecord::Base belongs_to :post file_column :image_path end The controller targets I

With a has_one/belongs_to relationship, what''s the best way to guarantee that the belongs_to object gets created and is accessible alongside the has_one object? I *think* the after_create callback is a good choice, but I discovered an oddity while trying it. F''rinstance, if every horse has a carriage: ============ ActiveRecord::Schema.define do create_table(:horses) {|t|

I''ve got an order model that stores order data. One piece of data is a credit card type, which is a digit 1,2 or 3. I have a cardType model that has an id, shortName and LongName for the credit card merchant (visa, mastercard, amex). I want to be able to say: order.cardType.shortName, but can''t seem to get has_one working. It works with has_many and a finder_sql statement on

I''m trying to build a system for generically storing an object graph, on top of AR itself. The idea is to define one base class, and use AR''s automatic single table inheritance to have it create the right class. Here''s what I have so far: table generic_objects: id int(11) not null auto_increment primary key type varchar(255) table generic_fields: id

There really doesn''t seem to be a *declarative* way to define a default value for belongs_to and has_one associations class Person < ActiveRecord::Base belongs_to :address end p = Person.new p.address.city = ''Atlantis'' # Bummer! Of course, there''s an easy way to avoid this class Person < ActiveRecord::Base belongs_to :address

So, I have 2 models A and B that share 5 common attributes and all other attributes are different. So I wanted to extract these 5 out into one common table and use has_one, belongs_to to knit it back together. So now there are 3 tables with 1 having the shared properties, we''ll call this table C. Table A id dollar_amount Table B id quantity_on_hand Table C id version My question is,

While I''m happy to continue talking about the vagaries of Rails deployments, I also need to actually build apps. :) I may have discovered a bit of a problem with :include as it applies to has_one associations. First, let me say that I''m a big fan of :include for reducing the number of SQL calls. There are times when I wish it could go more than 1 step away from the parent

I know you get a lot of questions like this, but I couldn''t find one which answers exactly what I''m after. I''m reasonably new to rails, and I''m having a bit of trouble with when to use belongs_to. On the rails wiki ( http://wiki.rubyonrails.org/rails/pages/belongs_to), it says "In general, the Foo model belongs_to :bar if the foo table has a bar_id foreign

Suppose I have one table: states id statename And I have two other tables that contains states: houses id color state_id places id place_name state_id How would my model relationships look like? class State < ActiveRecord::Base belongs_to house belongs_to place end class House < ActiveRecord::Base has_one state end class Place <

Every once in a while, I pipe up and whine that "belongs_to" should really be ''refers_to" [http://dev.rubyonrails.org/ticket/2130]. It''s time again. I''ve got a bunch of stuff going onto eBay, so, like any good engineer, I don''t just post it manually: I design a Rails-based inventory database that creates a semantically-correct XHTML/CSS auction

Hi to everyone, I have the following models: class Attachment < ActiveRecord::Base has_attachment :content_type => [:image, ''application/pdf''], :max_size => 3.megabytes, :path_prefix => ''../private/attachments'', :storage => :file_system, :processor => :rmagick,

I have a problem that surfaced in my attempt to upgrade my application to Rails 1.1. We have a STI model on the "belongs_to" side of a has_many/belongs_to relationship. All my unit tests for this model pass, and the relationships all seem to work fine. But in my functional tests, I''m getting errors. I''ve traced it back into the call to the has_many

Hi there, I''m currently building a membership application and I want to be able to select, not just all the memberships, but the most current membership from the database on a per user basis. I have linked the tables as shown:- class Membership < ActiveRecord::Base belongs_to :payment belongs_to :person end class Person < ActiveRecord::Base has_many :memberships

I have two models called entity and user. The entities table has a column called users_id that contains the user id of the user that created the entity. In entity I have... has_one :user ... as I want to be able to show the user who created the entity from the entity object. But this produces the following error... Mysql::Error: #42S22Unknown column ''users.entity_id'' in

Hey Guys, I''m getting a peculiar bug working with Observers and has_one associations. When a has_one association is invoked by an Observer it always returns null. I looked in the development.log file and the SQL for the has_one association isn''t even being executed. On the other hand, when I replace the has_one association with just a hand crafted method, it does get called