associations

问题 If anyone has a better title, please let me know :p I have the following models: class Car has_many :car_drivers has_many :drivers, :through => :car_drivers end class Driver has_many :car_drivers has_many :cars, :through => :car_drivers end class CarDriver belongs_to :car belongs_to :driver end Now I want to create a new Driver via Car, but the record in the join-table (car_drivers) should be created as well. I tried the following, but while the car record is created, the join-table record is

问题 I have question regarding associations in Ruby on Rails. In the application there are projects, users, roles and groups. The project belongs to a group with users, a user can belong to many different groups but can only have one specific role within that group. For example: In one group the user is the project owner, but in another group he is a writer. What is the best way to implement this using the built in functions in Rails? Thanks 回答1: Here is a very quick set of models that should

问题 I have found a Java example about how students register in a set of courses: Student-----takes------Courses and in the example is defined as Association, but why it cannot be Aggregation? for what I see each class could exist independently. How do differentiate both? In the above example I am dealing with the schema that a Student has an array of Courses as attribute, and Course has an array of Students within it also; so in that case is association because both of them are related, and

问题 Can you have a belongs_to belongs_to relationship in Rails? Search results gave me two results. The fact that I can't find very much info on the subject, seems to indicate that it shouldn't be done or is bad practice. I asked yesterday about a has_many relationship, but thought because I couldn't find information on this, I would generate a question so it is easier for people to search for this in the future. I'm paraphrasing another users answer (I hope this is ok). A Shoe can have many

问题 In a Rails app, I'm using FactoryGirl to define a general factory plus several more specific traits. The general case and all but one of the traits have a particular association, but I'd like to define a trait where that association is not created/built. I can use an after callback to set the association's id to nil , but this doesn't stop the association record from being created in the first place. Is there a way in a trait definition to completely disable the creation/building of an

问题 Simple model: class hat embedded_in :owner field :color end class owner embedds_one :hat referenced_in :house field :name end class house references_one :owner field :number end So simply puts, we have collection of houses that are associated to an owner, and the owner can have a colored hat. I can simply sort the house by their number: House.all.order_by( [[ :number, :asc ]]) But what I want is ordering the house, by the name of their owner, ideally I would like to write: House.all.order_by(

问题 I'm trying to add a new model to an existing model mesh. The existing one works perfectly but I can't get the new one to work properly and am wondering if the association is able to work the way I'm trying to make it work. Update: As I just got asked: belongs_to through was something I've read while gooling about the problem. If it doesn't exist, would has_one through be the correct way? I tried it as well but it also didn't work. Here is the existing mesh: class Course has_many :users,

问题 I'm trying to implement a Hibernate persistence layer in a Java application and I'm having some trouble with it. I'm encountering a no proxy error every time I attempt to access a simple, one way association. I haven't implemented Hibernate in quite the right way - I am using the thread method of Session control, which they do suggest you don't use for production. However, they use it in their tutorials. I am still trying to get the basics working, so I figured following the tutorials would

问题 In My React js application I need to pass data of my Product Model's association model(say "Taxon" ),i am doing it successfully using Active record serializer as ActiveModelSerializers::SerializableResource.new(object, options).serializable_hash where i pass options as all association relation. i can get whole array of taxon objects as json,But I want something mentioned As following i using rails as backed i am calling method like Prodct.first.category.name which gives => "mugs" the method

问题 I am getting the following error on my Rails 4.2 application. I'm trying to setup subscriptions with Stripe. A subscription belongs to a business and has_one plan. On my view I pass the params in the URL: http://localhost:3000/subscriptions/new?plan_id=2&business_id=1001 After I submit the form I get the error below and my code follows. Forgive me if this is a beginner question. Subscriptions Controller class SubscriptionsController < ApplicationController before_action :set_subscription,