I am using rails 4.2.0. and I am getting this error:
ActiveRecord::HasManyThroughAssociationNotFoundError:
Could not find the association :taggings in model Article
Here are my models:
class Tag < ActiveRecord::Base
has_many :taggings
has_many :articles, :through => :taggings
end
class Article < ActiveRecord::Base
has_many :comments
has_many :taggings
has_many :tags, :through => :taggings
end
class Tagging < ActiveRecord::Base
belongs_to :tag
belongs_to :article
end
Tagging is an intermediary model for the many-to-many relationship between Article and Tag.
And if it helps, my schema:
ActiveRecord::Schema.define(version: 20150224161732) do
create_table "articles", force: :cascade do |t|
t.string "title"
t.text "body"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "comments", force: :cascade do |t|
t.string "author_name"
t.text "body"
t.integer "article_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
add_index "comments", ["article_id"], name: "index_comments_on_article_id"
create_table "taggings", force: :cascade do |t|
t.integer "tag_id"
t.integer "article_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
add_index "taggings", ["article_id"], name: "index_taggings_on_article_id"
add_index "taggings", ["tag_id"], name: "index_taggings_on_tag_id"
create_table "tags", force: :cascade do |t|
t.string "name"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
end
I run this code in rails console to test my associations:
a = Article.first
a.tags.create name: "cool"
And I get the above error.
I have seen similar questions where the response "if you have through: :x, you have to have has_many :x first," but I don't think that is my issue.
This might be a silly question, but have you tried creating a Tagging independent of the Article model? If you haven't, than it could be something messed up with the database not having the Tagging model. Otherwise, associations look fine and should work. The only other thing I can think of is incorrect file names for your models folder
Related
migrate file exists but no model for rails application.There are user and book model.I created join table between user and book model.
I write console : rails g migration CreateJoinTableBooksUsers books users
rake:db migrate
**schema.rb**
create_table "books", force: :cascade do |t|
t.string "title"
t.string "author"
t.integer "page_count"
t.datetime "created_at", precision: 6, null: false
t.datetime "updated_at", precision: 6, null: false
t.boolean "status"
t.string "user_id"
t.boolean "barter_status"
end
create_table "books_users", id: false, force: :cascade do |t|
t.bigint "book_id", null: false
t.bigint "user_id", null: false
end
create_table "users", force: :cascade do |t|
t.string "email", default: "", null: false
t.string "encrypted_password", default: "", null: false
t.string "reset_password_token"
t.datetime "reset_password_sent_at"
t.datetime "remember_created_at"
t.datetime "created_at", precision: 6, null: false
t.datetime "updated_at", precision: 6, null: false
t.string "username"
t.index ["email"], name: "index_users_on_email", unique: true
t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
t.index ["username"], name: "index_users_on_username", unique: true
end
add_foreign_key "comments", "books"
add_foreign_key "comments", "users"
end
**migrate**
class CreateJoinTableBooksUsers < ActiveRecord::Migration[6.0]
def change
create_join_table :books, :users do |t|
t.index [:book_id, :user_id]
t.index [:user_id, :book_id]
end
end
end
A migration creates the tables in the database but doesn't create anything else.
But, for a true join table, you don't need a model:
https://guides.rubyonrails.org/association_basics.html#the-has-and-belongs-to-many-association
# app/models/user.rb
class User < ApplicationRecord
has_and_belongs_to_many :books
end
# app/models/books.rb
class Book < ApplicationRecord
has_and_belongs_to_many :users
end
IF you need scopes, callbacks, or methods on BooksUsers, you can use the has_many :through option:
https://guides.rubyonrails.org/association_basics.html#choosing-between-has-many-through-and-has-and-belongs-to-many
# app/models/user.rb
class User < ApplicationRecord
has_many :books_users
has_many :books, through: :books_users
end
# app/models/books.rb
class Book < ApplicationRecord
has_many :books_users
has_many :users, through: :books_users
end
In this case, you'll need to generate a model:
rails generate model BooksUsers
I want to fetch sku_code from products, wh_name from warehouses table and item_count from product_warehouses.
I tried something like
Product.all.includes(:product_warehouses)
But not working :(
Below are the schema of my tables
create_table "product_warehouses", force: :cascade do |t|
t.integer "product_id"
t.integer "warehouse_id"
t.integer "item_count"
t.integer "threshold"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.index ["product_id"], name: "index_product_warehouses_on_product_id"
t.index ["warehouse_id"], name: "index_product_warehouses_on_warehouse_id"
end
create_table "products", force: :cascade do |t|
t.string "sku_code"
t.string "name"
t.decimal "price"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "warehouses", force: :cascade do |t|
t.string "wh_code"
t.string "wh_name"
t.string "pin"
t.integer "max_cap"
t.integer "threshold"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
Below are the relationship between tables:
class Product < ApplicationRecord
has_many :product_warehouses
has_many :warehouses, through: :product_warehouses
end
class ProductWarehouse < ApplicationRecord
belongs_to :product
belongs_to :warehouse
end
class Warehouse < ApplicationRecord
has_many :product_warehouses
has_many :products, through: :product_warehouses
end
If you want to load all three records with a single query, use eager_load:
Product.all.eager_load(:product_warehouses, :warehouses)
Let's say you want to print sku_code, wh_name, and item_count in the console. First load all the products into variable:
products = Product.all.eager_load(:product_warehouses, :warehouses)
Then loop through the records and print out each of the values:
products.each do |product|
puts "sku_code: #{product.sku_code}"
product.product_warehouses.each do |product_warehouse|
puts "item_count: #{product_warehouse.item_count}"
puts "wh_code: #{product_warehouse.warehouse.wh_code}"
end
end
Having three models: Datum, Author, and Book .
class Datum < ApplicationRecord
has_many :authors
end
class Book < ApplicationRecord
belongs_to :author
end
class Author < ApplicationRecord
belongs_to :datum
has_many :books, dependent: :destroy
end
For exercise purpose, I wanted to model it that Datum(more general), can have many authors, which can have books.
After creating a datum object and an associated author for it, I could call nameofdatum.authors, but if I added a book to that author, it could not be recognized through nameofdatum.authors.books. Am I having wrong expectations ? (Should this be done with 'through'(an explanation of it would be much appreciated)
(Schema here if needed)
create_table "authors", force: :cascade do |t|
t.string "name"
t.integer "age"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.integer "book_id"
t.integer "datum_id"
t.index ["book_id"], name: "index_authors_on_book_id"
t.index ["datum_id"], name: "index_authors_on_datum_id"
end
create_table "books", force: :cascade do |t|
t.string "name"
t.string "book_type"
t.integer "pages"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.integer "author_id"
t.index ["author_id"], name: "index_books_on_author_id"
end
create_table "data", force: :cascade do |t|
t.string "region"
t.integer "budget"
t.date "aval"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
Should this be done with 'through'?
Yes, Datum has_many books through the authors assocition:
class Datum < ApplicationRecord
has_many :authors
has_many :books, through: :authors
end
And the books can be selected via:
Datum.last.books
It's actually selects books using the following query:
SELECT "books".* FROM "books" INNER JOIN "authors" ON "authors"."id" = "books"."author_id" WHERE "authors"."datum_id" = ?
If you want to add a new book through author, you have to assign an author. So you can try:
nameofdatum.author.books.build ....
your codenameofdatum.authors.books, you can't use a plural(author) to add a new book.
Hope to help you.
In my app User can have many Companies and vice versa. In Accounts table id of User and id of its Company is stored.
I want to find all Users who belong to Companies, which belong to current_user. Let's assume that the current_user is like master User (not Admin, as that would be system Admin) of those companies.
How do I do this? My guess is to do it with Arel, but then how should it look in Model, Controller, View? Many thanks for any help. I'm on Rails 5.
models/user.rb
class User < ApplicationRecord
has_many :accounts, dependent: :destroy
has_many :companies, through: :accounts
models/account.rb
class Account < ApplicationRecord
belongs_to :company
belongs_to :user
accepts_nested_attributes_for :company, :user
models/company.rb
class Company < ApplicationRecord
has_many :accounts, dependent: :destroy
has_many :users, through: :accounts
accepts_nested_attributes_for :accounts, :users
My schema.rb looks like this:
create_table "accounts", force: :cascade do |t|
t.integer "company_id"
t.integer "user_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.index ["company_id"], name: "index_accounts_on_company_id"
t.index ["user_id"], name: "index_accounts_on_user_id"
end
create_table "companies", force: :cascade do |t|
t.string "name"
t.string "legal_name"
t.string "reg_number"
t.string "address"
t.string "bank_acc"
t.string "description"
t.string "website"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.integer "role", default: 0
t.integer "currency", default: 0
end
create_table "users", force: :cascade do |t|
t.string "name"
t.string "email"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.string "password_digest"
t.string "remember_digest"
t.boolean "admin", default: false
t.index ["email"], name: "index_users_on_email", unique: true
end
You can find current user's companies, and eager load users who belong to those companies
#companies = current_user.companies.includes(:users)
To list all users(may be in a view), loop through #companies and all its users
#companies.each do |company|
company.users.each do |user|
puts user.name
end
end
Or use map/collect to assign them to a variable.
#users = #companies.map(&:users).flatten
Hello I do have this two models and I would like to check that my model associations are working the way it should trough rails console.
I am not able to do the association work. The relationship is the following:
One Event has one rule and one rule belongs to one event. It could not be a rule without an event and it could not be a event without a rule.
Any idea how to test this with rails console?
MODEL 1:
class Event < ActiveRecord::Base
has_and_belongs_to_many :users
has_one :rule
has_many :grand_prixes
belongs_to :eventable, polymorphic: :true
end
MODEL 2
class Rule < ActiveRecord::Base
belongs_to :events
end
Rules' Schema:
create_table "rules", force: :cascade do |t|
t.boolean "abs"
t.boolean "tc"
t.boolean "allow_auto_clutch"
t.boolean "allow_sc"
t.boolean "allow_throttle_blip"
t.boolean "dynamic_track"
t.integer "damage_mult"
t.integer "fuel_rate"
t.integer "tyre_wear_rate"
t.integer "quali_percentage"
t.integer "min_valid_laps"
t.integer "event_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
add_index "rules", ["event_id"], name: "index_rules_on_event_id"
Events' Schema:
create_table "events", force: :cascade do |t|
t.string "event_type"
t.string "name", null: false
t.datetime "starting_date"
t.datetime "ending_date"
t.integer "eventable_id"
t.string "eventable_type"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
add_index "events", ["eventable_type", "eventable_id"], name: "index_events_on_eventable_type_and_eventable_id"
Thanks in advance.
I think your belongs_to :events should be singular to follow the rails convention :
class Rule < ActiveRecord::Base
belongs_to :event
end
The conventional name of a relation is always singular for belongs_to and has_one, and always plural for has_many.
Related documentation : http://guides.rubyonrails.org/association_basics.html#belongs-to-association-reference
EDIT : There much left to say
You wrote :
ev = Event.create(:name "test1").save
rule = Rule.create.save
create is already a new followed by a save. No need to save afterwards.
the syntax key: value is something very common in ruby, and should be well understood : you're actually writing a hash, equivalent to {:key => value}, but the syntax allows you to write key: value ONLY IF your key is a Symbol.
the columns eventable_type and eventable_id should be in the table rules, who is hosting the polymorphic relation with eventable things. Event should not have these columns, and event_id should not exist at all in rules.
Here's an example of what you can write in your console to create an Event and a Rule :
ev = Event.create(name: "test1")
rule = Rule.create(abs: true, event: ev)
Change your code:
class Rule < ActiveRecord::Base
belongs_to :event
end
With belongs_to you should use singular like event not events.
In console you can check association like:
Event.first.rule if Event.first.present?
For more details you should go through http://guides.rubyonrails.org/association_basics.html documentation.
Current code:
class Rule < ActiveRecord::Base
belongs_to :event
end
class Event < ActiveRecord::Base
has_and_belongs_to_many :users
has_one :rule
has_many :grand_prixes
belongs_to :eventable, polymorphic: :true
end
SCHEMA:
create_table "rules", force: :cascade do |t|
t.boolean "abs"
t.boolean "tc"
t.boolean "allow_auto_clutch"
t.boolean "allow_sc"
t.boolean "allow_throttle_blip"
t.boolean "dynamic_track"
t.integer "damage_mult"
t.integer "fuel_rate"
t.integer "tyre_wear_rate"
t.integer "quali_percentage"
t.integer "min_valid_laps"
t.integer "event_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
add_index "rules", ["event_id"], name: "index_rules_on_event_id", unique: true
create_table "events", force: :cascade do |t|
t.string "event_type"
t.string "name", null: false
t.datetime "starting_date"
t.datetime "ending_date"
t.integer "eventable_id"
t.string "eventable_type"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
add_index "events", ["eventable_type", "eventable_id"], name: "index_events_on_eventable_type_and_eventable_id"
Tested on console:
ev = Event.create(:name "test1").save
rule = Rule.create.save
No idea how to link it both through console.