has-many-through

问题 I have an (I think) relatively straightforward has_many :through relationship with a join table: class User < ActiveRecord::Base has_many :user_following_thing_relationships has_many :things, :through => :user_following_thing_relationships end class Thing < ActiveRecord::Base has_many :user_following_thing_relationships has_many :followers, :through => :user_following_thing_relationships, :source => :user end class UserFollowingThingRelationship < ActiveRecord::Base belongs_to :thing belongs

问题 Just ran into an issue with a has_many :through association and after/before-destroy callbacks not being triggered. Say, I have users, groups, and an intermediate relation called membership. I have a form that allows users to be enrolled into groups by creating a new membership record when they check off associated checkboxes. Basically an array of group_ids. Looks something like this: Which group would you like to join? (check all that apply) [] Group A [] Group B [] Group C And I wish to

问题 I've read the documentations and tons of tutorials about the has_many :through relations in Rails but I can't for the life of me get the hang of it. I'm trying to add a group to my current_user(devise) and I have a table in between Group and User with a status(The user's status is changeable for that group). Whenever I create a new Group now I get an error saying uninitialized constant Group::GroupUser here are my models: groupuser.rb class GroupUser < ActiveRecord::Base belongs_to :group

问题 Consider the following models: class Person(models.Model): name = models.CharField(max_length=128) class Group(models.Model): name = models.CharField(max_length=128) members = models.ManyToManyField(Person, through='Membership') class Membership(models.Model): person = models.ForeignKey(Person) group = models.ForeignKey(Group) date_joined = models.DateField() invite_reason = models.CharField(max_length=64) Membership is a customized many-to-may through object with extra fields. If I have a

问题 I am trying to retrieve an activerecord object from my db. My models are class User < ActiveRecord::Base belongs_to :account has_many :domains, :through => :account end And class Account < ActiveRecord::Base has_many :domains has_many :users end And class Domain < ActiveRecord::Base belongs_to :account end Now I would like to retrieve a user based on the username and a domain name (lets assume that these are attributes of the User and the Domain classes respectively). i.e. something along the

问题 I'm new to rails and I've been trying to get two has_many :though relationships to work out (as opposed to using has_and_belongs_to_many as explained by this post http://blog.flatironschool.com/post/35346328762/why-you-dont-need-has-and-belongs-to-many) but am now running into a Postgres error: PG::Error: ERROR: column reference "id" is ambiguous LINE 1: ...on_id" IS NULL AND "components"."id" = 1 ORDER BY id ASC LIM... ^ : SELECT 1 AS one FROM "components" INNER JOIN "collection_components"

问题 I'm playing with an example from Rails Guides: http://guides.rubyonrails.org/association_basics.html#the-has_many-through-association This example has the following setup for the models: class Physician < ActiveRecord::Base has_many :appointments has_many :patients, :through => :appointments end class Appointment < ActiveRecord::Base belongs_to :physician belongs_to :patient end class Patient < ActiveRecord::Base has_many :appointments has_many :physicians, :through => :appointments end I'm

问题 I've read multiple questions about this, but have yet to find an answer that works for my situation. I have 3 models: Apps , AppsGenres and Genres Here are the pertinent fields from each of those: Apps application_id AppsGenres genre_id application_id Genres genre_id The key here is that I'm not using the id field from those models. I need to associate the tables based on those application_id and genre_id fields. Here's what I've currently got, but it's not getting me the query I need: class

问题 A Person can have many Events and each Event can have one polymorphic Eventable record. How do I specify the relationship between the Person and the Eventable record? Here are the models I have: class Event < ActiveRecord::Base belongs_to :person belongs_to :eventable, :polymorphic => true end class Meal < ActiveRecord::Base has_one :event, :as => eventable end class Workout < ActiveRecord::Base has_one :event, :as => eventable end The main question concerns the Person class: class Person <

问题 I have a Task model associated to a Project model via has_many through and need to manipulate the data before delete/insert via the association. Since "Automatic deletion of join models is direct, no destroy callbacks are triggered." i can not use callbacks for this. In Task i need all project_ids to calculate a value for Project after Task is saved. How can i disable delete or change delete to destroy on has_many through association? What is best practise for this problem? class Task has