has_one nested attributes not saving

Question

I have two models Project and ProjectPipeline.

I want to create a Project form that also has fields from the ProjectPipeline model. I have created the form successfully but when I hit save the values aren't stored on the database.

project.rb

class Project < ActiveRecord::Base

  has_one :project_pipeline

  accepts_nested_attributes_for :project_pipeline

  self.primary_key = :project_id
end

projectpipeline.rb

class ProjectPipeline < ActiveRecord::Base

  belongs_to :project, autosave: :true

  validates_uniqueness_of :project_id

end

I don't always want a project pipeline but under the right conditions based on a user viewing a project. I want the project pipeline fields to be built, but only saved if the user chooses to save/populate them.

So when the project is shown I build a temporary project pipeline using the project_id: from params[:id] (not sure if I really need to do this). Then when the project is saved I use the create_attributes. But if it has already been created or built I just want to let the has_one and belongs_to association kick in and then use update_attributes.

My issue is when I am trying to save, I am either hitting a 'Forbidden Attribute' error if I use params[:project_pipeline] or having nothing saved at all if I used project_params. I have checked and rechecked all my fields are in project_params and even tried using a project_pipeline_params but that didn't feel right.

It is driving me nuts and I need to sleep.

projects_controller.rb

def show
  @project = Project.find(params[:id])
  if @project.project_pipeline
  else
    @project.build_project_pipeline(project_id: params[:id])
  end
  autopopulate
end



def update
    @project = Project.find(params[:id])
    if @project.project_pipeline
    else
      @project.build_project_pipeline(project_id: params[:id], project_type: params[:project_pipeline][:project_type], project_stage: params[:project_pipeline][:project_stage])
    end
    if @project.update_attributes(project_params)
      flash[:success] = "Project Updated"
      redirect_to [@project]
    else
      render 'edit'
    end
  end


def project_params
  params.require(:project).permit(:user_id, project_pipeline_attributes:[:project_id,:project_type,:project_stage,
      :product_volume,:product_value,:project_status,:outcome, :_destroy])
end

show.html.haml

    - provide(:title, "Show Project")
%h1= @project.project_title
= simple_form_for(@project) do |f|
  = f.input  :id, :as => :hidden, :value => @project, :readonly => true  
  = f.input :user_id, label: 'Assigned to Account Manager', :collection => @account_managers, :label_method => lambda { |r| "#{r.first_name} #{r.last_name}" }
  = f.input :project_id, :readonly => true
  = f.input :status, :readonly => true
  = f.input :project_stage, :readonly => true

  - if @project.project_codename = "project pipeline"
    = simple_fields_for @project.project_pipeline do |i|
      %h2 Project Pipeline
      - if @project.user_id == current_user.id
        = i.input :project_volume, label: 'Project Status', collection: @project_status
        = i.input :project_value, label: 'Project Status', collection: @project_status
        = i.input :project_status, label: 'Project Status', collection: @project_status
      = i.input :outcome, label: 'Outcome', collection: @outcome


    = f.submit 'Save'

If you've gotten this far I sincerely thank you.

Answer 1

I'm not sure from your description if this is the problem, but one the thing is that a update_attributes with a has_one, by default, will rebuild the children(!), so you would lose the attributes you initialised. You should provide de update_only: true option to accepts_nested_attributes_for. You can find more on this here, in the rails docs. The line would be this:

accepts_nested_attributes_for :project_pipeline, update_only: true

Considering the after_initialize, that would result in every project always having a pipeline. While that could be desirable, it isn't necessarily, depending on your domain, so I'd be a bit careful with that.

Cheers, Niels

Answer 2

Solution

You need to change few things here. Firstly:

= simple_fields_for @project.project_pipeline do |i|

When you pass the object, rails have no idea it is to be associated with the parent object and as a result will create a field named project[project_pipeline] instead of project[project_pipeline_attributes]. Instead you need to pass the association name and call this method on the form builder:

= f.simple_fields_for :project_pipeline do |i|

This will check find out that you have defined project_pipeline_attributes= method (using accept_nested_attributes_for` and will treat it as association. Then in your controller change your show action to:

def update
  @project = Project.find(params[:id])
  @project.assign_attributes(project_params)
  if @project.save
    flash[:success] = "Project Updated"
    redirect_to @project
  else
    render 'edit'
  end
end

And all should work. As a separate note, since you are allowing :_destroy attribute in nested params, I am assuming you want to be able to remove the record using nested attributes. If so, you need to add allow_destroy: true to your accepts_nested_attributes_for call.

Now a bit of styling:

You can improve your show action a bit. First of all, I've noticed you are building an empty pipeline in every single action if none has been declared yet. That mean that you probably should move this logic into your model:

class Project < AR::Base

  after_initalize :add_pipeline

  private

  def add_pipeline
    project_pipeline || build_project_pipeline
  end
end

You also have the mysterious method prepopulate - most likely it should be model concern as well.

Another point: This syntax:

if something
else
  # do sth
end

is somehow quite popular and makes the code unreadable as hell. Instead, use:

if !something
  # do something
end

or (preferred)

unless something
  # do something
end