How do I make the relationship many for many in Ruby on Rails with has and belongs to Many?

Asked

Viewed 817 times

2

I have a table system and a table category, a system has many categories and a category has several systems, I wanted to use the has_and_belongs_to_many option of Rails (for being a simple relation and even to learn how to use this resource). But I am doubtful on the following question, I have to create a migrate that manages a table that stores these relations or type Rails itself takes care of it, by placing the has_many_and_belong_to :systems and has_many_and_belong_to :categories?

Has anyone used, or has any suggestion/tip on how to do?

System controller method

def sistem_params
  params.require(:sistem).permit(:description, :categories)
end

Modelo Sistemas

class Sistem < ActiveRecord::Base
  has_and_belongs_to_many :categories

  has_many :versions
end

model Category

class Category < ActiveRecord::Base
  has_and_belongs_to_many :sistems

  has_many :tests
end

Table migration connecting models

class CategoriesAndSistems < ActiveRecord::Migration
  def change
    create_table :categories_sistems do |t|
      t.references :category, :sistem
    end
  end
end
ruby-on-rails table relational-model rails4
  • 1

    I don’t have time now to answer, but yes, migration has to be done when using has_many_and_belongs_to. You can see this better here: http://railscasts.com/episodes/47-two-many-to-many

  • I was able to create the migrate, the table, and in the console associate system with category, but I still could not do it in the controller and in the view. In the system create/Edit view I want to be able to select in a select multiple the categories it has, and when saving it creates the association, currently by the console it lets associate more than once a category for a system. I am also having problem in the system parameters, I tried to add categoriano (controler), tried nested Attributes and is not working it does not let receive the categories I am trying to select in the form

  • How are you sending this information to the back end? Put models/migrations with the relationship parts so I can better understand the problem.

  • I added the codes to the description of the question @Gabrielkatakura, need some other part?

  • Have you tried category_ids (passing only an array of Ids) instead of categories?

  • post schema.db after migrate for us to see please

Show 1 more comment

1 answer

0


You create a table categories_systems

create_table :categorias_sistemas, id: false do |t|
  t.belongs_to :categoria, index: true
  t.belongs_to :sistema, index: true
end

and both in the Category class you will add the 

has_and_belongs_to_many :sistemas

And in the System class

has_and_belongs_to_many :categorias

http://guides.rubyonrails.org/association_basics.html#the-has-and-belongs-to-Many-Association

I suggest taking care of classes in Portuguese because the pluralization of Rails usually gets weird.

Browser other questions tagged ruby-on-rails table relational-model rails4

You are not signed in. Login or sign up in order to post.