Access parent attribute in child model rails

Question

Working on creating a conditional validation for my model. To check for this I need to check if the Parent.parent_attribute == "true"

validates :departure_date, presence: true, future: true, :if => :awesome_method?
 belongs_to :parent


 def awesome_method?
   if @parent.parent_attribute == "true"
     true
   else
     false
   end
 end

Currently @parent.parent_attribute is returning nil even though the payload has it. I think I'm running into an issue where it can't access the parent_attribute because it hasn't saved yet... How do I perform a check that the parent has a value before setting a validation?

Update For clarity's sake, I am creating the parent and the child simultaneously. When I try to use Parent.find... I get back

Couldn't find Parent with 'parent_id'=CORRECT_INVOICE_NAME

Update 2 There is a create in both the parent and the child but the following JSON is what creates the parent with child.

{
 “parent": {
   “parent_id": "PLZDONTSAVE",
   “data": 2525.25,
   “parent_attribute": true,

   “child_attributes":[
     { “child_toy": “123",
       “child_data": “ABC" }
   ]
 }
}

Parent controller

  def create
    @parent = Parent.new(parent_params)
    if @parent.save
      render json: @parent, status: :created, location: @parent
    else
      render json: @parent.errors, status: :unprocessable_entity
    end
  end

  def parent_params
    params.require(:parent).permit(:parent_id, :parent_attribute,
    child_attributes:[:child_toy, :child_data, ])
  end

score 4 · Accepted Answer · answered Apr 21 '16 at 21:12

4

Unless you define @parent somewhere, it will be nil, just as @foo and @bar. You can access an object linked via an association (like your belongs_to) by simply using parent without the "@".

So try this:

  def awesome_method?
    parent.parent_attribute == "true"
  end

answered Apr 21 '16 at 21:12

tbreier

214
1
8

`parent.parent_attribute` is returning > NoMethodError (undefined method `parent_attribute' for nil:NilClass) – CheeseFry Apr 21 '16 at 21:42
Hm, can you show the code in which you create the parent and the child simultaneously? – tbreier Apr 21 '16 at 22:18
updated my question to demonstrate what I mean by simultaneously building the objects – CheeseFry Apr 22 '16 at 13:47
Ah I see. Looks like you figured it out, too! :-) – tbreier Apr 22 '16 at 17:58

score 3 · Answer 2 · edited May 23 '17 at 12:23

3

I got it to work by updating both models with the following. With help from here

In the child model

belongs_to :parent, inverse_of: :child

In the parent model

accepts_nested_attributes_for :children
has_many :children, inverse_of: :parent

That coupled with @tbreier's suggestion got the job done.

edited May 23 '17 at 12:23

Community

1
1

answered Apr 22 '16 at 16:44

CheeseFry

1,299
1
21
38

Access parent attribute in child model rails

2 Answers2