Mongoid不坚持协会

Question

Consider the following:

class Parent
  include Mongoid::Document
  field:name
  references_one :child

  before_create :initialize_child

  protected

  def initialize_child
    self.child = Child.create
  end

end

class Child
  include Mongoid::Document
  field:name
  referenced_in :parent
end

In a console, i get the following weird behavior:

> p = Parent.create
 => #<Parent _id: 4d811748fc15ea355d00000b, name: nil> 
> p.child
 => #<Child _id: 4d811748fc15ea355d00000c, name: nil, parent_id: BSON::ObjectId('4d811748fc15ea355d00000b')> 

All good so far. Now when I try to fetch the parent, and then find the child -- no luck ...

> p = Parent.last
 => #<Parent _id: 4d811748fc15ea355d00000b, name: nil> 
> p.child
 => nil 

This happens for me with both mongoid rc6 and rc7

Am I doing something wrong (I am new to mongoid) or this a bug? Any work arounds?

Thanks!!

Jonathan

Answer 1

Since the child isn't embedded, it won't auto-save it on its own

Try

class Parent
  include Mongoid::Document
  field:name
  references_one :child, autosave: true 

  before_create :initialize_child

  protected
  def initialize_child
    self.child ||= Child.new
  end
end

Also -- you may be expected the Child to be embedded in the Parent document. If so, you'll want to switch to "embedded_in"