Rails association method errors - ruby-on-rails

Question

In my ruby on rails application i've applied a relationship between two table: Article and Category with a relation has_and_belongs_to_many.
class Category < ActiveRecord::Base
has_and_belongs_to_many :articles
end
class Article < ActiveRecord::Base
has_and_belongs_to_many :categories
end
I'm following this tutorial for implement a Has_many system with the checkboxes (Railcast)
i've write this part:
<% for category in Category.all%>
<div>
<%= check_box_tag "article[category_ids][]", category.id, #article.categories.include?(category) %>
<%= category.name %>
</div>
<% end %>
but i've got this error :
Mysql2::Error: Table 'CMS_development.articles_categories' doesn't exist: SHOW FULL FIELDS FROM articles_categories
Where am i wrong?
EDIT ADDING THE MIGRATION AND THE SCHEMA
MIGRATION:
class AddCategoryToArticles < ActiveRecord::Migration
def change
add_reference :articles, :category, index: true, foreign_key: true
end
end
SCHEMA:
ActiveRecord::Schema.define(version: 20151001153131) do
create_table "articles", force: :cascade do |t|
t.boolean "published"
t.boolean "on_evidance"
t.boolean "foreground"
t.string "title", limit: 255
t.string "subtitle", limit: 255
t.datetime "date"
t.text "body", limit: 65535
t.text "small_body", limit: 65535
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.integer "category_id", limit: 4
end
add_index "articles", ["category_id"], name: "index_articles_on_category_id", using: :btree
create_table "categories", force: :cascade do |t|
t.string "name", limit: 255
t.text "description", limit: 65535
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
add_foreign_key "articles", "categories"
end

Answer 1

Two issues:
You don't have the join table articles_categories
You're not referencing the categories correctly
Firstly, to use a has_and_belongs_to_many association, you need to invoke the appropriate join table:
Your schema shows, quite clearly, that you don't have this. As stated in other answers, you need to create a schema as follows:
class CreateArticlesCategories < ActiveRecord::Migration
def change
create_table :articles_categories, id: false do |t|
t.references :articles
t.references :categories
end
end
end
This will give you the join table which you'll be able to populate with your select box...
--
For your checkbox, you can do the following:
#app/views/articles/new.html.erb
<%= form_for #article do |f| %>
<%= f.collection_select :categories, Category.all, :id, :name %>
<%= f.submit %>
<% end %>
To populate this through the controller, you'd need to use the following:
#app/controllers/articles_controller.rb
class ArticlesController < ApplicationController
def new
#article = Article.new
end
def create
#article = Article.new article_params
#article.save
end
private
def article_params
params.require(:article).permit(:title, :categories)
end
end

Answer 2

You should write and execute a migration for creating articles_categories table:
class CreateArticleCategory < ActiveRecord::Migration
def change
create_table :articles_categories do |t|
t.references :articles
t.references :categories
end
end
end