Rails fields_for and not creating relationship with nested object

Question

The model "Formula" has many "Operands" created using a simple_nested_form, using fields for. It seems the process is correct, and no errors launched, but operands are not saved.

Formula model:

class Formula < ActiveRecord::Base
  attr_accessible :name, :client_id
  validates_presence_of :name, :client_id
  belongs_to :client
  has_many :operands, as: :operation, dependent: :destroy
  accepts_nested_attributes_for :operands, allow_destroy: true
  attr_accessor :operator, :numeric_operand, :operation_id, :operation_type
end

Operand model:

class Operand < ActiveRecord::Base
  attr_accessible :operator, :numeric_operand, :operation_id, :operation_type
  validates_presence_of :operator
  belongs_to :operation, polymorphic: true
  OPERATOR_TYPES = ["+", "-", "*", "/"]
end

Formulas controller:

class FormulasController < ApplicationController
  load_and_authorize_resource
  def new 
    @formula.operands.build 
  end

  def create
    @formula = Formula.new(params[:formula])      
    @formula.client_id = @current_client.id unless @formula.client_id.present?
      if @formula.save
        redirect_to @formula, notice: t('controllers.notice.successfully_created') }
      else
        render action: "new" 
      end
    end

  def edit
  end

  def update
      if @formula.update_attributes(params[:formula])
       redirect_to @formula, notice: t('controllers.notice.successfully_updated')
      else 
        render action: "edit"
      end
  end

Formula _form:

= simple_nested_form_for @formula, :html => { :class => 'form-vertical' } do |f|    
  = f.error_notification
 .form-inputs
    .row   
      .span3= f.input :name  
    .well      
      = f.fields_for :operands   
      = f.link_to_add t('helpers.links.add'), :operands  
  .form-actions
    = f.button :submit, :class => 'btn-primary', disable_with: "#{t('helpers.links.submitting')}"

_operands_fields:

.well
  .row
    .span2= f.input :operator, collection: Operand::OPERATOR_TYPES
    .span3= f.input :numeric_operand

This all seem to work fine, but when the proccess ends, no operands are created. When inspecting returned params in update or create methods using better errors, operands attributes are retrieved successfully from the form, but the relationship between formula and them is not created:

>> @formula.operands.all
=> #<ActiveRecord::AssociationRelation []>
>> @formula.operands.first
=> nil
>> params
=> {"utf8"=>"✓", "_method"=>"patch", "authenticity_token"=>"--TOKEN--", "formula"=>{"name"=>"Sdfg", "operands_attributes"=>{"1457352032591"=>{"operator"=>"+", "numeric_operand"=>"3"}}}, "commit"=>"Update Formula", "action"=>"update", "controller"=>"formulas", "locale"=>"en", "id"=>"3"}
>>

Seems like you are not using strong params, so I guess you are using Rails 3. Can you try .save! instead of .save? So that errors are raised (in case there are), and not silently fail. — Jay-Ar Polidario
– Jay-Ar Polidario, Commented Mar 7, 2016 at 12:43
I use Rails 4, but the gem 'protected_attributes' lets me handle accessibility in a Rails 3 way. I have tried using .save! but the issue persist. — Prade Mismo
– Prade Mismo, Commented Mar 7, 2016 at 12:50

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

Update (Using Strong Params)

Continuing from our discussion that protected_attributes doesn't work with nested attributes for a polymorphic association in Rails 4 (unverified), I then suggested to use strong params:

class FormulasController < ApplicationController
  # ..
  def formula_params
    params.require(:formula).permit(:name, :client_id, operands_attributes: [ :id, :operator, :numeric_operand, :formula_id, :_destroy ])
  end
  # ..
end

edited Jun 20, 2020 at 9:12

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answered Mar 7, 2016 at 12:55

Jay-Ar Polidario

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10 Comments

Prade Mismo Over a year ago

Wow, such a lapsus... Ok, I've added this, and now operands are created... But all attributes are set to nil.

Jay-Ar Polidario Over a year ago

Your Operand model has attr_accessible :operand, :numeric_operand, so those attributes should have been sanitized already. I am not sure why you're getting nil. I can only guess that maybe the polymorphic association has something to do with this.

Prade Mismo Over a year ago

I've tried it with a non polymorphic relationship and it seems to work fine... This is a great inconvenience :(

Jay-Ar Polidario Over a year ago

@PradeMismo, you might want to try strong params for this. Maybe the protected_attributes gem does not support sanitizing polymorphic association. I imagine it has already been deprecated in favor of strong params, which might be the reason of some bugs / incompatibilities. Maybe other user know how to deal with this though. I haven't really used protected_attributes since Rails 3

Prade Mismo Over a year ago

Any help about strong parameters? tried this

def formula_params     params.require(:formula).permit(:name, :client_id, operands_attributes: [ :operator, :numeric_operand, :formula_id ])   end

thing, but still getting ActiveModel::ForbiddenAttributesError.

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