Hi,
I want to set a relation without _id reference.
I want to save, for example the key in the related document.

class Brand
include Mongoid::Document

field :name, type: String
field :key, type: Symbol

has_many :products
end
class Product
include Mongoid::Document

field :name, type: String
field :key, type: Symbol

belongs_to :marca
end

ProductDocument

Unknown macro: { _id}

For me is not important the key of the relation, only value.

Thanks.