CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-4mongoidruby-on-rails-4.2
Gardezi
Gardezi

Reputation: 2842

Has_and_belong_to_many relation with the same model

I am trying to implement a has_and_belong_to_many relation with the same model, but I don't know how.

For Example, a user should be able to follow other users.

Also, I have multiple fields of the same model in that model; how would I give it another name?

Upvotes: 0

Views: 105

Answers (1)

Sheharyar
Sheharyar

Reputation: 75740

There are two scenarios and two different implementations:

The 'Friends' model

Let's say one User can have many :friends where each friend is also an object of the User model. You can do it this way:

has_and_belongs_to_many :friends, class_name: 'User'

This tells rails that an object of User class can have a many-to-many relation with itself as friends. So you can call something like this:

@user_a.friends
#=> [@user_x, @user_y, @user_z]  # Array of User Objects

@user_x.friends
#=> [@user_a, @user_b, @user_c]  # Array of User Objects

The 'Followers/Following' model

Let's say one User can follow other users as well have other users follow him. This is how you'll implement it:

has_many   :followers, class_name: 'User', inverse_of: :following
belongs_to :following, class_name: 'User', inverse_of: :followers

This tells rails that each user can have many followers which is an Array of other User objects, and that user is accessible to others as an object in the following array. For example, if @user2 follows @user1, it would look like this:

@user1.followers
#=> [@user2, @user3]

@user2.following
#=> [@user1]

Upvotes: 1

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