Has_many through and belongs to in Rails - ruby-on-rails

I am working on a Rails app where a User can create a magazine and another user can subscribe to that magazine. I want to know the best way to do this.
Currently I have a subscription model that builds from current user when created and users the current magazine as the magazine_id. This allow me to have a table of user_ids and magazine_ids. This allows me to see all the subscriptions but it means I cant easily check all the magazines someone subscribes to or check all the subscribers of a magazine.
When I try to use has_many :through, it throws up an error with building from current user. I have put in the relevant code below, hopefully it covers it all and thanks in advance.
User model:
class User < ActiveRecord::Base
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
has_many :magazines
has_many :subscriptions
end
Subscription model:
class Subscription < ActiveRecord::Base
belongs_to :user
belongs_to :magazine
end
Magazine model:
class Magazine < ActiveRecord::Base
belongs_to :user
has_many :subscrptions
has_many :users
end
The snippet of code from the subscription controller that throws up the error when I use has many through
def new
#subscription = current_user.subscriptions.build
#sub = Sub.find(params[:sub_id])
end
Hopefully that is enough for someone to figure out, if not please ask me for the other code or information.

You're very close, you're just missing the connection. Magazine can see Subscription because Subscription has its magazine_id. User can see Subscription because Subscription has its user_id. Through the Subscription, Magazine and User can see each other. So you want to user through
class User < ActiveRecord::Base
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
has_many :magazines, through: :subscriptions
has_many :subscriptions
end
class Subscription < ActiveRecord::Base
belongs_to :user
belongs_to :magazine
end
class Magazine < ActiveRecord::Base
belongs_to :user
has_many :subscriptions
has_many :users, through: :subscriptions
end
If this doesn't work, make sure you post your schema.rb/relevant fields from the tables you mentioned.

I think this should work, might need to set additional options though.
User model:
class User < ActiveRecord::Base
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
has_many :magazines
has_many :subscriptions
has_many :subscribed_magazines, through: :subscriptions, source: :magazine
end
Subscription model:
class Subscription < ActiveRecord::Base
belongs_to :user
belongs_to :magazine
end
Magazine model:
class Magazine < ActiveRecord::Base
belongs_to :user
has_many :subscriptions
has_many :subscribed_users, through: :subscriptions, source: :user
end
Edit: Needed source, not class_name

Related

Querying for values from several models

I have a Course and Lesson models. Course has several lessons. I want to find all the lessons for currently logged in student to generate kind of timetable.
I have a method that returns all the courses that this student is studying. Now I want to get all lessons from all those courses in #courses into #lessons, something like:
def index
#courses = current_student.find_courses
#lessons = #courses.lessons
end
Is it possible to do it somehow simple on one line?
The find_courses method is implemented as following:
def find_courses
Course.where("id IN (?)", StudentAssignment.select("course_id").where('student_id == (?)', self.id))
end
The Models:
class Student < ApplicationRecord
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :validatable
has_many :student_assignments
has_many :courses, :through => :student_assignments
....
class Lesson < ApplicationRecord
belongs_to :room
belongs_to :teacher
belongs_to :course
....
class Course < ApplicationRecord
has_many :lessons, dependent: :destroy
has_many :teacher_assignments
has_many :teachers, :through => :teacher_assignments
has_many :student_assignments
has_many :students, :through => :student_assignments
...
class Student < ApplicationRecord
has_many :courses
def active_lessions
Lession.joins(course: :students).where(students: {id: self.id})
end
end
In this way you can directly get all active lesssions for current_user
current_student.active_lessions
Try:
#lessons = #courses.flat_map(&:lessons)
It takes each course in #courses list and gets the list of lessons for that course.

Devise will not save to database due to belongs_to relationship

After adding the marked line to my Devise user model in a Rails app I can no longer create new users in either the web form or using User.create() on the console. Commenting out this line restores full functionality. Obviously it is very closely related to the line above, it is so that I can have users assigned to a dealership. Any suggestions how to fix or do it differently as I need this functionality?
class User < ApplicationRecord
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable, :recoverable, :rememberable, :trackable, :validatable, :registerable
has_many :tanks, dependent: :destroy
has_many :properties, dependent: :destroy
has_many :contacts, dependent: :destroy
has_many :stations
has_many :clients, :class_name => 'User', :foreign_key => :manager_id
belongs_to :dealer, :class_name => 'User' #<--- this one
end
belongs_to :dealer, :class_name => "User",foreign_key: "dealer_id", optional: true
Note: - make sure you should have dealer_id in User model also to make it working #user.dealer if #user.dealer.present?
Reason
In Rails 5, whenever we define a belongs_to association, it is required to have the associated record present by default.

Forced validations for associated fields

I am using rails 5.0.0.1
When I submit a form, validations for associated fields are coming into action.
I have Gig, User, Category and other models
I am using devise for user authentication
Gig model
class Gig < ActiveRecord::Base
has_many :proposals
belongs_to :category
has_many :abilities
has_many :skills, through: :abilities
belongs_to :user
end
User model
class User < ApplicationRecord
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
has_many :gigs
has_many :proposals
end
Category model
class Category < ActiveRecord::Base
has_many :gigs
end
When I try to create the gig in console, the transaction rolls back.
the error messages are
["Category must exist", "User must exist"]
I appreciate your help. Thanks in advance.
In rails 5 when you add belongs_to it makes this field required. Try this
belongs_to :user, optional: true

User has_many association not working (error:Could not find the association :user_categories in model Category)

I have three models and here they are when I try to create a has_many. I basically want my users (using devise) to have many categories. And categories to have many users.
user.rb
class User < ActiveRecord::Base
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable,
:omniauthable
has_many :user_categories
has_many :categories, through: :user_categories
acts_as_messageable
def mailboxer_email(object)
email
end
end
userCategory.rb
class UserCategory < ActiveRecord::Base
belongs_to :user
belongs_to :category
accepts_nested_attributes_for :categories
end
Category.rb
class Category < ActiveRecord::Base
has_many :user_categories
has_many :user, through: :user_categories
validates :name, presence: true, length: {minimum: 3, maximum: 25}
validates_uniqueness_of :name
end
when I run category.users << user I get this error:
ActiveRecord::HasManyThroughAssociationNotFoundError: Could not find the association :user_categories in model Category
I can't say for sure what the problem could be, but a few things I could point out:
UserCategory's accepts_nested_attributes_for, does that mean the you want to be able to dynamically create categories?
Category has_many :users, through: :user_categories, not user
You need to follow the Rails file naming conventions, user.rb, user_category.rb and category.rb
These may not be the problem/solution, but I believe they're in the way of resolving the problem.

Associations not working

When a user cancels their account on my application their user record is correctly removed from the database but their profile record still seems to exist. Below are my models for user and profile, any solutions?
Profile.rb
class Profile < ActiveRecord::Base
belongs_to :user
end
user.rb
class User < ActiveRecord::Base
has_one :profile
#callback that creates a profile for each user that signs up
after_create :create_profile
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
private
def create_profile
self.profile = Profile.create
end
end
You have to specify explicitly what to do with dependent model.
As example
has_one :profile, dependent: :destroy
There are some other options like :delete, :nullify. You can take a look at them here: http://apidock.com/rails/ActiveRecord/Associations/ClassMethods/has_one
It will also delete the association too.
has_one :profile, dependent: :destroy
source: http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html

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