CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-4has-manyhas-and-belongs-to-manybelongs-to
sapA
sapA

Reputation: 11

rails 4 belongs_to and has_many to the same model

I have an Opportunity model that belongs_to Section model. Section has_many opportunities.

class Opportunity < ActiveRecord::Base

  belongs_to :section

class Section < ActiveRecord::Base

  has_many :opportunities

Opportunity model has to have section_id but i would like to be able to also have many sections as involved sections in some cases.

how would it be possible to create? thanks

Upvotes: 0

Views: 55

Answers (1)

Rajdeep Singh
Rajdeep Singh

Reputation: 17834

You need a many-to-many association between, Opportunity and Section, for that you need to create a connecting table between the two, create a migration 

create_table :opportunities_sections, id: false do |t|
  t.belongs_to :opportunity
  t.belongs_to :section
end

Then in Opportunity model, add this line

has_and_belongs_to_many :sections

In Section model, add this line

has_and_belongs_to_many :opportunities

Finally, remove section_id column from opportunities table.

More info on has_and_belongs_to_many association here

https://guides.rubyonrails.org/association_basics.html#the-has-and-belongs-to-many-association

You can also achieve many-to-many association via has_many through association, the basic difference between has_and_belongs_to_many and has_many through is you can create a model class for the connecting table, that way you get more flexibility in terms of saving any additional data with the connection. More info here

https://guides.rubyonrails.org/association_basics.html#the-has-many-through-association

What to choose?

https://guides.rubyonrails.org/association_basics.html#choosing-between-has-many-through-and-has-and-belongs-to-many

Rails guides got all the answers!

Upvotes: 1

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