I have Product and Categories models.
Each Product can have many Categories. Each category will have many products.
Am I better off doing 2 HABTM or has_many relations?
I have been told that HABTM is being deprecated - is that true?
Also, for both, I assume I will have to use a join table categories_products. How do I create that? Just a regular migration?
Thanks.
Example of top(number). Updated.
class Product < ActiveRecord::Base
has_many :category_products do
def with_categories
includes(:category)
end
end
has_many :categories, :through => :category_products
def top_categories(number)
category_products.with_categories.order("purchases_count DESC").limit(number).map {|c| c.category} # category included
end
end
class Category < ActiveRecord::Base
has_many :category_products do
def with_products
includes(:product)
end
end
has_many :products, :through => :category_products
def top_products(number)
category_products.with_products.order("purchases_count DESC").limit(number).map {|c| c.product} # product included
end
end
class CategoryProduct < ActiveRecord::Base
belongs_to :product
belongs_to :category
validates_uniqueness_of :product_id, :scope => :category_id
# attribute :purchases_count, :default => 0
end
Related
So, I'm trying to create a product categorization 'system' in my rails 4 app.
Here's what I have so far:
class Category < ActiveRecord::Base
has_many :products, through: :categorizations
has_many :categorizations
end
class Product < ActiveRecord::Base
include ActionView::Helpers
has_many :categories, through: :categorizations
has_many :categorizations
end
class Categorization < ActiveRecord::Base
belongs_to :category
belongs_to :product
end
Also, what gem should I use? (awesome_nested_set, has_ancestry)
Thanks!
This is what I did in one of my projects which is live right now and works very well.
First the category model, it has a name attribute and I am using a gem acts_as_tree so that categories can have sub categories.
class Category < ActiveRecord::Base
acts_as_tree order: :name
has_many :categoricals
validates :name, uniqueness: { case_sensitive: false }, presence: true
end
Then we will add something called a categorical model which is a link between any entity(products) that is categorizable and the category. Note here, that the categorizable is polymorphic.
class Categorical < ActiveRecord::Base
belongs_to :category
belongs_to :categorizable, polymorphic: true
validates_presence_of :category, :categorizable
end
Now once we have both of these models set up we will add a concern that can make any entity categorizable in nature, be it products, users, etc.
module Categorizable
extend ActiveSupport::Concern
included do
has_many :categoricals, as: :categorizable
has_many :categories, through: :categoricals
end
def add_to_category(category)
self.categoricals.create(category: category)
end
def remove_from_category(category)
self.categoricals.find_by(category: category).maybe.destroy
end
module ClassMethods
end
end
Now we just include it in a model to make it categorizable.
class Product < ActiveRecord::Base
include Categorizable
end
The usage would be something like this
p = Product.find(1000) # returns a product, Ferrari
c = Category.find_by(name: 'car') # returns the category car
p.add_to_category(c) # associate each other
p.categories # will return all the categories the product belongs to
I have following three models
class Rating < ActiveRecord::Base
belongs_to :user
belongs_to :book
end
class User < ActiveRecord::Base
attr_accessible :name, :dob, :mobile
has_many :books, :through => 'ratings'
end
class Book < ActiveRecord::Base
attr_accessible :book_name, :author, :pages
has_many :users, :through => 'ratings'
end
Now I have to find all the "book_name"s of each book which is related the respective user and store it in the array.
Here is code
#book_names = []
#books = Rating.find(:all, 'user_id = ?', current_user.id)
#books.each do |book|
book_info = Book.find(book.id)
#book_names << book_info.book_name
end
Is there any other way for the same or join method.
Yes, there is simple way to do it. Try
#book_names= current_user.books.map(&:book_name)
In my Rails application I have people which can have many projects and vice versa:
# app/models/person.rb
class Person < ActiveRecord::Base
has_many :people_projects
has_many :projects, :through => :people_projects
end
# app/models/people_project.rb
class PeopleProject < ActiveRecord::Base
belongs_to :person
belongs_to :project
end
# app/models/project.rb
class Project < ActiveRecord::Base
has_many :people_projects
has_many :people, :through => :people_projects
def self.search(person_id)
if person_id
where("person_id = ?", person_id) # not working because no person_id column in projects table
else
scoped
end
end
end
How can I filter the projects by person_id in the index view of my ProjectsController, e.g. by using a URL like this: http://localhost:3000/projects?person_id=164
I can't get my head around this. Please help! Thanks...
Your association definition is not complete for Person and Project models. You also need has_many :people_projects defined.
# app/models/person.rb
class Person < ActiveRecord::Base
has_many :people_projects # <-- This line
has_many :projects, :through => :people_projects
end
# app/models/project.rb
class Project < ActiveRecord::Base
has_many :people_projects # <-- This line
has_many :people, :through => :people_projects
end
# app/models/people_project.rb
# This is defined correctly
class PeopleProject < ActiveRecord::Base
belongs_to :person
belongs_to :project
end
Please reference The has_many :through Association for further details.
With this definition, you will be able to get all the projects of the current user using current_user.projects, just like you've already done in your ProjectsController#index.
Update:
You could use either joins or includes in your search method and apply the where condition. Something like follows:
# app/models/project.rb
class Project < ActiveRecord::Base
has_many :people_projects
has_many :people, :through => :people_projects
def self.search(person_id)
if person_id
includes([:people_projects, :people]).where("people.id = ?", person_id)
else
scoped
end
end
end
You will not have a person_id in the projects table because its a has_many<>has_many relationship.
Simply #person.projects will perform a join btw person_projects & projects tables and returns the appropriate projects.
*I assume,current_user returns a Person object.*
Also, complete your Model definitions. Each of them should list their relation to PeopleProjects
class Person < ActiveRecord::Base
has_many :people_projects
has_many :projects, :through => :people_projects
end
class Project < ActiveRecord::Base
has_many :people_projects
has_many :people, :through => :people_projects
end
I have a quite complicated relation between models and are now frustrated by a SQL Query to retrieve some objects.
given a Product model connected to a category model via a has_many :through association and a joint table categorization.
Also a User model connected to this category model via a has_many :through association and a joint table *category_friendship*.
I am now facing the problem to retrieve all products, which are within the categories of the array user.category_ids. However, I can't just not manage to write the WHERE statement properly.
I tried this:
u = User.first
uc = u.category_ids
Product.where("category_id IN (?)", uc)
However this won't work, as it doesn't have a category_id in the product table directly. But how can I change this to use the joint table categorizations?
I'm giving you the model details, maybe you find it helpful for answering my question:
Product.rb
class Product < ActiveRecord::Base
belongs_to :category
def self.from_users_or_categories_followed_by(user)
cf = user.category_ids
uf = user.friend_ids
where("user_id IN (?)", uf) # Products out of friend_ids (uf) works fine, but how to extend to categories (cf) with an OR clause?
end
Category.rb
class Category < ActiveRecord::Base
has_many :categorizations
has_many :products, through: :categorizations
has_many :category_friendships
has_many :users, through: :category_friendships
Categorization.rb
class Categorization < ActiveRecord::Base
belongs_to :category
belongs_to :product
Category_friendship.rb
class CategoryFriendship < ActiveRecord::Base
belongs_to :user
belongs_to :category
User.rb
class User < ActiveRecord::Base
has_many :category_friendships
has_many :categories, through: :category_friendships
def feed
Product.from_users_or_categories_followed_by(self) #this should aggregate the Products
end
If you need more details to answer, please feel free to ask!
Looking at the associations you have defined and simplifying things. Doing a bit refactoring in what we have to achieve.
Product.rb
class Product < ActiveRecord::Base
belongs_to :category
end
User.rb
class User < ActiveRecord::Base
has_many :categories, through: :category_friendships
scope :all_data , includes(:categories => [:products])
def get_categories
categories
end
def feed
all_products = Array.new
get_categories.collect {|category| category.get_products }.uniq
end
end
Category.rb
class Category < ActiveRecord::Base
has_many :users, through: :category_friendships
has_many :products
def get_products
products
end
end
NO NEED OF CREATING CATEGORY_FRIENDSHIP MODEL ONLY A JOIN TABLE IS NEEDED WITH NAME CATEGORIES_FRIENSHIPS WHICH WILL JUST HAVE USER_ID AND CATEGORY_ID
USAGE: UPDATED
Controller
class UserController < ApplicationController
def index
#all_user_data = User.all_data
end
end
view index.html.erb
<% for user in #all_user_data %>
<% for products in user.feed %>
<% for product in products %>
<%= product.name %>
end
end
end
I've upvoted Ankits answer but I realized there is a more elegant way of handeling this:
given:
u = User.first
uc = u.category_ids
then I can retrieve the products out of the categories by using:
products = Product.joins(:categories).where('category_id IN (?)', uc)
I just created a counter_cache field and the controller looks like this.
#users = User.where(:sex => 2).order('received_likes_count')
The association in User.rb is
has_many :received_likes, :through => :attachments, :source => :likes, :dependent => :destroy
Problem is that counter_cache is declared in the belong_to of Like.rb and I don't know how to tell it that is for the has_many :through association.
belongs_to :user, :counter_cache => :received_likes
You have previous
class Product
has_and_belongs_to_many :categories
end
class Category
has_and_belongs_to_many :products
end
and migration
class CreateCategoriesProducts < ActiveRecord::Migration
def change
create_table :categories_products, id: false do |t|
t.references :category
t.references :product
end
add_index :categories_products, [:category_id, :product_id]
end
end
now change all to
class Product
has_many :categories_products, dependent: :destroy
has_many :categories, through: :categories_products
end
class Category
has_many :categories_products, dependent: :destroy
has_many :products, through: :categories_products
end
and new one
class CategoriesProduct < ActiveRecord::Base
# this model uses table "categories_products" as it is
# column products_count is in the table "categories"
belongs_to :category, counter_cache: :products_count
belongs_to :product
end
According to this post (from last month) and this post (from 2008), it doesn't seem to be possible. However, the latter post does have code for a workaround (copy/paste'd from that link for your convenience, credit goes to DEfusion in the second link)
class C < ActiveRecord::Base
belongs_to :B
after_create :increment_A_counter_cache
after_destroy :decrement_A_counter_cache
private
def increment_A_counter_cache
A.increment_counter( 'c_count', self.B.A.id )
end
def decrement_A_counter_cache
A.decrement_counter( 'c_count', self.B.A.id )
end
end
(This is for a scheme where C belongs_to B, B belongs_to A, A has_many C :through => B
This basically does the same thing:
after_save :cache_post_count_on_tags
def cache_post_count_on_tags
tags.each {|t| tag.update_attribute(:posts_count, t.posts.size)}
end
And you need a posts_count column on tags, or whatever associations you have.