Rails 5, Simple Fields For with Cocoon gem for nested resources

Question

I am trying to learn how to use namespaced routes.

I have a model called Proposal and another called Innovation. The associations are:

Proposal

has_many :innovations
    accepts_nested_attributes_for :innovations, reject_if: :all_blank, allow_destroy: true

Innovation

belongs_to :proposal

In my routes.rb, I have:

resources :proposals do 
    resources :innovations

In my proposals controller, I have:

def new
    @proposal = Proposal.new
    @proposal.innovations.build

    # authorize @proposal
  end

  def edit
    @proposal.innovations_build unless @proposal.innovations

  end

In my proposal form, I am trying to nest the form fields for the innovation model.

<%= f.simple_fields_for [@proposal, @innovation] do |f| %>
        <%= f.error_notification %>
          <%= render 'innovations/innovation_fields', f: f %>

      <% end %>

      <%= link_to_add_association 'Add another novel aspect', f, :innovations, partial: 'innovations/innovation_fields' %> 
      </div>  

When I try this, I get an error that says:

undefined method `model_name' for nil:NilClass

I get the same error when I try:

  <%= f.simple_fields_for [@proposal, @innovations] do |f| %>

Can anyone see what I need to do in order to have the proposal form include the innovation form fields?

Answer 1

You are using nested-attributes, so in this particular case there is no need for nested routes. You can just write

<%= f.simple_fields_for @proposal do |f| %>

This will post the form, containing all the innovations, to the ProposalsController.