How do I create a parent record from the child when the parent doesn't exist?

Question

I've trying to model books, chapters, and notes.

I have the following:

class Book < ApplicationRecord
    has_many :chapters
    has_many :notes
end

class Chapter < ApplicationRecord
    belongs_to :book
    has_many :notes
end

class Note < ApplicationRecord
    belongs_to :chapter
end

I can create Books and notes just fine.

What I want to do when creating a new Note is either create a new Chapter or assign an existing one to a note . Said another way: I'm trying to create a parent from the child before the parent even exists, or assigning an exising parent to the child.

This is the kind of functionality that's provided by gems such as acts_as_taggable_on . I've tried using nested forms, but just couldn't get it near to what I wanted. I'm wondering if my architecture is even correct for this type of use? Any guidance you could provide would be much appreciated.

Answer 1

In your create method in your NotesController you could do something like

parent_chapter = Chapter.find_or_create_by(name: 'How To Program')
# parent_chapter is now either the existing chapter by that name or a new one
new_note = Note.new(params[:note])
new_note.chapter = parent_chapter # or new_note.chapter_id = parent_chapter.id
new_note.save

The method find_or_create_by I think is what you needed here. If that method is depreciated in your rails version, tryfirst_or_create , like this

parent_chapter = Chapter.where(name: 'How To Program').first_or_create