CODEWITHSUNDEEP
ruby-on-railsrubymongodbdatabase-designmongoid
atomAltera
atomAltera

Reputation: 1781

has_many relation via IDs list in parent

I got in trouble while designing data model.

I have master object "A" with its children "B", and "B" has many "C", but some "C" can also be free (not belong to any "B").

By standard mas_many/belongs_to Mongoid relationd foreign key stores in "C". And it's not so awful, it works fine even when it orphan, but I think it's not looks good. Is there any way make Mongoid to store children IDs in parent's list field?

Upvotes: 0

Views: 550

Answers (2)

MatayoshiMariano
MatayoshiMariano

Reputation: 2096

For future viewers....

I ended using:

And in the before_add callback from the has_and_belongs_to_many, I added something like object_to_add.c_id ||= self.id. This way you can have the IDs listed in the parent.

Example with a Playlist with multiple Categories:

class Playlist
  has_and_belongs_to_many :categories, before_add: :add_playlist_id, inverse_of: :playlist

  private

  def add_playlist_id(category)
    category.playlist_id ||= id
  end
end


class Category
  belongs_to :playlist, inverse_of: :categories
end

Upvotes: 0

Nikita Chernov
Nikita Chernov

Reputation: 2061

What you describe sounds like belongs to many and there is a way to achieve that by using has_and_belongs_to_many relation on B class.

But in my opinion your initial approach is semantically better, but its up to you to choose.

Upvotes: 1

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