has_one relationships don’t have id only getters or setters. For example engineer.laptop_id or engineer.laptop_id= are not implemented in Rails 5. Is there any reason for this?
class Engineer < ActiveRecord::Base belongs_to :team has_one :laptop has_many :tasks end
engineer = Engineer.first
engineer.team_id # works engineer.laptop_id # doesnt work (Not implemented) engineer.task_ids # work
``
Thanks
Shishir
No, because belongs_to is for when the foreign key lives on the record with the association and has_one is when the foreign key lives on the associated model instead.
Ypu can’t have the _id setter on the model with the association because there is no such field on the model or underlying table.
That is because there is no laptop_id in Engineer (assuming engineer has_one laptop). Laptop has an engineer_id. You can do engineer.laptop.id
Colin
has_many relationship also has the foreign key in another table in the above example it would be in the tasks table. Regardless it has an accessor only for ids of related tasks engineer.task_ids.
Similarly, Shouldn’t has_one also have accessors for id even if its in another table?
I think it makes sense. Note that there are a whole other methods that exist on has_many relations that do not have equivalent on has_one:
clear
empty?
size
etc (see: ActiveRecord::Associations::ClassMethods vs ActiveRecord::Associations::ClassMethods)
But I think this is intentional… has_one associations are tricky and hard to “fit” into a novices mindset.
Having getters like .association_id would only make things more complicated when the programmer bangs their heads against the wall because .association_id = 123.
Keep up to date with Rails on Twitter and This Week in Rails
Policies: Conduct, License, Maintenance, Security, Trademarks