single-table-inheritance

问题 I have implemented inheritance hierarchy using SINGLE_TABLE with SecondaryTables. This works otherwise, but when my secondary table's field(s) are empty (= null in Oracle), next update to the entity fails since Hibernate thinks it should INSERT to the table when it should UPDATE. Example: CREATE TABLE TASK ( ID NUMBER(10) NOT NULL , TYPE NUMBER(1) NOT NULL , STATUS NUMBER(1) NOT NULL , CONSTRAINT TASK_PK PRIMARY KEY (ID) ENABLE); CREATE TABLE SUB_TASK ( ID NUMBER(10) NOT NULL , TEXT VARCHAR2

问题 I have a has_many relationship between two entities, Feeds and Posts. I also have specific types of posts, Videos and Photos. This is structured in the database using single table inheritance. Right now I have my Feed model specifying a has_many relationship between Feeds and Posts (including the subtypes) class Feed < ActiveRecord::Base has_many :posts has_many :photos has_many :videos Is there a better, more conventional way to specify this? Or is what I have as simple as it can get? 回答1:

问题 I hardly see any pointer on the following problem related to Hibernate. This pertains to implementing inheritance using a single database table with a parent-child relationship to itself. For example: CREATE TABLE Employee ( empId BIGINT NOT NULL AUTO_INCREMENT, empName VARCHAR(100) NOT NULL, managerId BIGINT, CONSTRAINT pk_employee PRIMARY KEY (empId) ) Here, the managerId column may be null, or may point to another row of the Employee table. Business rule requires the Employee to know about

问题 I have the following classes: Project Person Person > Developer Person > Manager In the Project model I have added the following statements: has_and_belongs_to_many :people accepts_nested_attributes_for :people And of course the appropriate statements in the class Person . How can I add a Developer to a Project through the nested_attributes method? The following does not work: @p.people_attributes = [{:name => "Epic Beard Man", :type => "Developer"}] @p.people => [#<Person id: nil, name:

问题 I dont know how to create a worker and a association. So i am able to link those together. I have a type colulm in user. This is my form(http://localhost:3000/workers/sign_up): <h2>Create Worker</h2> <%= form_for(resource, :as => resource_name, :url => registration_path(resource_name)) do |f| %> <%= devise_error_messages! %> <p><%= f.label :email %><br /> <%= f.text_field :email %></p> <p><%= f.label :kodeord %><br /> <%= f.password_field :password %></p> <p><%= f.label :bekraeft_kodeord %>

问题 Our organization is looking to standardize on Entity Framework once v4 comes out. As a result, I am looking at what it would take to migrate our application that uses NHibernate for persistence to EF4 using POCO support. In a couple of places we use single table inheritance (also known as Table Per Hierarchy). I have been unable to get it to work using the following. Payment (base class [should be abstract but having trouble there as well]) CreditCardPayment (concrete implementation)

问题 I have a Model Property which has subclasses using STI, and which I would like all to use the same controller with only different view partials depending on the subclass. Property Restaurant < Property Landmark < Property It works find except I'm not sure how to discern the subclass inside the controller to render the correct view. Ie. /restaurants works and goes to the properties controller but I can't tell that they want the Restaurant subclass? map.resources :restaurant, :controller =>

问题 I am having an issue with searching for records in my STI table due to my inheritance structure class User < ActiveRecord::Base class LegacyUser < User class AuthUser < User class SuperUser < AuthUser class FieldUser < AuthUser class ClientAdmin < AuthUser The problem is that find does not work for the AuthUser Model. The query is looking for type "AuthUser" and does not include the other three possibilities. Edit: While playing around with this it started to work but only for ClientAdmin and

问题 After switching to Rails 3, I noticed that I have to reboot my server to make STI model classes reload with each request. For example, suppose I have this: # app/models/vehicle.rb class Vehicle < ActiveRecord::Base end # app/models/car.rb class Car < Vehicle end If I make a change to Vehicle , the change is loaded on the next request. But if I make a change to Car , I have to reboot my server for it to load. Any ideas on fixing this? I'm running WEBrick, but I'm not committed to it. 回答1: We

问题 I want to use Single Table Inheritance using a column other than type . According to the Rails documentation - http://api.rubyonrails.org/classes/ActiveRecord/Base.html, I can do this by modifying ActiveRecord::Base.inheritance_column . How can I do this? 回答1: Try the following: class MyModel < ActiveRecord::Base self.inheritance_column = 'column_that_is_not_type' end Your migrations should work everywhere. 回答2: @Vidya's answer is correct but a better way is: class MyModel < ActiveRecord: