I was following the answer laid out at the link below to set up a many_to_many relationships on my Rails 4 app. (New to rails, here.)
Implement "Add to favorites" in Rails 3 & 4
I have Users and Exercises, and I want users to be able to have Favorite Exercises. I created a join table called FavoriteExercise with user_id and exercise_id as columns. I've got it populating, and it seems to be working fine, but I'm not able to use it to call directly to my favorites.
Meaning, I want to type:
user.favorite = #list of exercises that have been favorited
I get this error when I try to load that list in my browser:
SQLite3::SQLException: no such column: exercises.favorite_exercise_id:
SELECT "exercises".* FROM "exercises" INNER JOIN "favorite_exercises"
ON "exercises"."favorite_exercise_id" = "favorite_exercises"."id"
WHERE > "favorite_exercises"."user_id" = ?
My models:
class User < ActiveRecord::Base
has_many :workouts
has_many :exercises
has_many :favorite_exercises
has_many :favorites, through: :favorite_exercises, source: :exercises
class Exercise < ActiveRecord::Base
belongs_to :user
has_many :workouts, :through => :exercises_workouts
has_many :favorites
has_many :favorited_by, through: :favorite_exercises, source: :exercises
class FavoriteExercise < ActiveRecord::Base
has_many :exercises
has_many :users
I just tried switching FavoriteExercise to 'belongs_to' instead of 'has_many, because it seems maybe that's the way that should go? but then I get this error:
uninitialized constant User::Exercises
Just trying to figure out how to set up the tables and associations so I can call .favorites on a user and get all their favorites.
If you want the list of exercises of the user and at the same, the list of favorite exercise of the user, then I think your join table should just be users_exercises wherein it will list all the exercises by the users. To list the favorite exercises, just add a boolean field indicating if the exercise is a user favorite and add a :scope to get all the favorite exercises.
So in your migration file:
users_exercises should have user_id, exercise_id, is_favorite
Then in your model:
class User < ActiveRecord::Base
has_many :workouts
has_many :users_exercises
has_many :exercises, through: :users_exercises
scope :favorite_exercises, -> {
joins(:users_exercises).
where("users_exercises.is_favorite = ?", true)
}
class Exercise < ActiveRecord::Base
has_many :workouts, :through => :exercises_workouts
has_many :users_exercises
has_many :users, through: :users_exercises
class UsersExercise < ActiveRecord::Base
belongs_to :exercise
belongs_to :user
You just need to simplify your model logic as follow:
class User < ActiveRecord::Base
has_many :workouts
has_many :exercises
has_many :favorite_exercises
has_many :favorites, through: :favorite_exercises, class_name: "Exercise"
class Exercise < ActiveRecord::Base
belongs_to :user
has_many :workouts, :through => :exercises_workouts
has_many :favorite_exercises
has_many :favorited_by, through: :favorite_exercises, class_name: "User"
class FavoriteExercise < ActiveRecord::Base
belongs_to :favorited_by
belongs_to :favorite
Then you can call user.excercises or excercise.users in your User/Excercise instance.
user.excercises = #list of exercises that have been favorited
Is that the many-to-many relationship you want?
Related
i have a simple data set-up with a model for Users and a model for Tasks.
Between these two models i have two has_many :through associations: Fellowships and Assignements. In total i want to specify for a task several followers and several assignees.
I now want to display for a specific task all assignees and all followers.
If there would only be one association I simply could do #task.users. As i have two associations i want to specify by which association i want to get all users.
See my code:
class User < ActiveRecord::Base
has_many :assignments
has_many :tasks, through: :assignments
has_many :fellowships
has_many :tasks, through: :fellowships
end
class Task < ActiveRecord::Base
has_many :assignments
has_many :users, through: :assignments
has_many :fellowships
has_many :users, through: :fellowships
end
class Assignment < ActiveRecord::Base
belongs_to :user
belongs_to :task
end
class Fellowship < ActiveRecord::Base
belongs_to :user
belongs_to :task
end
Let's assume i have a task as
#task = Task.first
I now want to have all assignees and all followers with something like
#assignees = #task.users "over association assignment"
#followers = #task.users "over association followship"
but i don't know how to do this.
Thanks for the help!
You can write in following way.
has_many :assignment_tasks ,through: :assignments ,source: :task
has_many :fellowship_tasks, through: :fellowships, source: :task
So I have an app in which users can create cars. They can also like cars and I want to create an association between both. Cars that they created belong to them and Cars that they have liked belong to them through the context of liking them. To do this I have set up my associations as follows:
User Association:
class User < ActiveRecord::Base
has_many :cars
has_many :cars, -> {distinct}, through: :likes
end
Car Association:
class Car < ActiveRecord::Base
belongs_to :users
has_many :likes
has_many :users, -> { distinct }, through: :likes
end
Like Association:
class Like < ActiveRecord::Base
belongs_to :user
belongs_to :car
end
The problem is that before I had my user has_many cars through like relationship declared. I used to be able to call #user.cars and it would present the user's cars. Now it returns the collection of the cars the user has liked. I need methods for each collection.
When I try: User.likes.cars
I get a
No Method error
and the console log looks through the likes records and still doesn't return the cars even though my likes records have a car_id field.
I have looked at a bunch of questions but have trouble understanding them. I've also tried to define methods in the model and nothing is seeming to work. Any help is appreciated.
How would I be able to change my associations so I can have a for query both User.cars (for cars the user has created) and User.likes.cars (for cars the user has liked)?
So the below answer from Oleg didn't work exactly but led me in the right direction. Thank you! I started by following the above example and doing:
class User < ActiveRecord::Base
has_many :cars
has_many :car_likes, -> {distinct}, class_name: 'Car', through: :likes
end
class Car < ActiveRecord::Base
belongs_to :users
has_many :likes
has_many :user_likes, -> { distinct }, class_name: 'User', through: :likes
end
This returned the following error in console:
ActiveRecord::HasManyThroughSourceAssociationNotFoundError: Could not find the source association(s) "car_likes" or :car_like in model Like. Try 'has_many :car_likes, :through => :likes, :source => '. Is it one of user or car?
So I changed it to:
class User < ActiveRecord::Base
has_many :cars
has_many :car_likes, -> {distinct}, through: :likes, source: :cars
end
Car Association:
class Car < ActiveRecord::Base
belongs_to :users
has_many :likes
has_many :user_likes, -> { distinct }, through: :likes, source: :users
end
It nows works for both models! Thanks and hopefully this is helpful to someone else with the same problem.
has_many :cars, -> {distinct}, through: :likes overrides has_many :cars because it redefines User.cars. Try the following:
class User < ActiveRecord::Base
has_many :cars
has_many :car_likes, -> {distinct}, class_name: 'Car', through: :likes
end
Car Association:
class Car < ActiveRecord::Base
belongs_to :users
has_many :likes
has_many :user_likes, -> { distinct }, class_name: 'User', through: :likes
end
#To get them, instead of user.likes.cars
#user.car_likes
#car.user_likes
Please let me know if the problem persists. There might be another error.
I don't see where you are defining any model as polymorphic.
In the past I have done something like this.. actually I did this for tags/taggings and made "like" a tag a user applied to another instance. This is an ad-hoc modification and I may have missed something but it's a pretty common use case for polymorphic associations.
class Like < ActiveRecord::Base
belongs_to :likeable, polymorphic: true
...
end
class Liking < ActiveRecord::Base
belongs_to :like
belongs_to :likeable, :polymorphic => true
end
class User < ActiveRecord::Base
has_many :likings, :as => :likeable
has_many :likes, -> { order(created_at: :desc) }, :through => :taggings
end
I am struggling to find the easiest solution for associating three models:
User
Organization
Role
User and Organization is a HABTM association - one user can have multiple organizations and vice versa.
One user can also have multiple roles, but just one per organization.
Right now I have this in my model:
user.rb
class User < ActiveRecord::Base
has_many :roles, through: :organizations
has_and_belongs_to_many :organizations, :join_table => :organizations_users
end
organization.rb
class Organization < ActiveRecord::Base
has_and_belongs_to_many :users, :join_table => :organizations_users
has_many :roles
end
role.rb
class Role < ActiveRecord::Base
has_many :users, through: :organizations
belongs_to :organizations
end
Does that make sense?
Here are my though:
Given that you're using the has_and_belongs_to_many and given Rails' defaults, your specification of the join_table is redundant
Your has_many :roles, through: :organizations will only work if you have both a role and a user field in the organizations tables, as Rails will expect to do a SQL select of that table looking for those fields.
Since you want users to have up to one one role per organization, then I would think the most straightforward thing would be to add a role field to the organizations_users model, as follows:
user.rb
class User < ActiveRecord::Base
has_many :roles, through: :organizations_users
has_many :organizations, :through => :organizations_users
has_many :organizations_users
end
organization.rb
class Organization < ActiveRecord::Base
has_many :users, :through => :organizations_users
has_many :roles, :through => :organizations_users
has_many :organizations_users
end
organization_user.rb
class OrganizationUser < ActiveRecord::Base
belongs_to :user
belongs_to :organization
belongs_to :role
end
role.rb
class Role < ActiveRecord::Base
end
The above assumes that you have some reason to want Role to continue to be an ActiveModel as opposed to just a string field in the organizations_users table.
I have models User, Team, Document. There's a many-to-many relationship between Users and Teams, and a many-to-many relationship between Teams and Documents, using join tables called TeamMembership and TeamDocument respectively.
The relationships in my models look like this:
class Document < ActiveRecord::Base
has_many :team_documents, dependent: :destroy
has_many :teams, through: :team_documents
end
class User < ActiveRecord::Base
has_many :team_memberships, dependent: :destroy, foreign_key: :member_id
has_many :teams, through: :team_memberships
has_many :documents, through: :teams
end
class TeamDocument < ActiveRecord::Base
belongs_to :team
belongs_to :document
end
class TeamMembership < ActiveRecord::Base
belongs_to :team
belongs_to :member, class_name: "User"
end
class Team < ActiveRecord::Base
has_many :team_documents, dependent: :destroy
has_many :documents, through: :team_documents
has_many :team_memberships, dependent: :destroy
has_many :members, through: :team_memberships
end
The idea is that users can belong to many teams, a document can be associated with many teams, and users will only have access to documents that "belong" to at least one team that the user is a member of.
Here's the question: I can use User#documents to retrieve a list of all the documents that this user is allowed to view. But this will return duplicates if a document is viewable by more than one team which the user is a member of. How can I avoid this?
I know I can remove the duplicates after the fact with #user.documents.uniq, but as I will never want to include the duplicates in any case, is there a way I can just make #documents not include duplicates every time?
I don't have nested has_many :through like yours to test it, but I suspect using uniq option on your user association would help :
class User < ActiveRecord::Base
has_many :documents, through: :teams, uniq: true
end
You can add a default_scope on Document model:
class Document < ActiveRecord::Base
default_scope group: { documents: :id }
Book has_and_belongs_to_many Students
Student has_and_belongs_to_many Books
In BooksStudents model I want to add "status" field to store if it is rented, bought ..etc. and be able to select for example #student.books.rented or #student.books.where(:books_students=>{:status=>2})
Can I do that with HABTM?
AFAIK no, you will need a has_many :through setup..
class Book < ActiveRecord::Base
has_many :books_students
has_many :students, :through => :books_students
end
class BooksStudent < ActiveRecord::Base
belongs_to :book
belongs_to :student
end
classStudent < ActiveRecord::Base
has_many :books_students
has_many :books, :through => :books_students
end
so you can do something like #student.books or #student.student_books.where(:status =>2)