Creating a nested object/modal from an existing nested object/modal in Ruby on Rails

Question

I am using deeply nested model in my project (using simple_form and cocoon). Everything works fine as long as all nested objects are new.

My problem is, that I want to create a nested object from an existing (nested) object.

Here is my model

class Application < ActiveRecord::Base
    belongs_to :submitter
    has_one :composition

    accepts_nested_attributes_for :submitter, :composition
end

class Submitter < ActiveRecord::Base
    has_one :spouse
    has_many :children
    has_many :receipts
    has_many :applications

    accepts_nested_attributes_for :spouse, :children, :receipts, :applications
end

class Child < ActiveRecord::Base
    belongs_to :submitter
    has_many :receipts
end

The working process looks like this:

new Application --> new Submitter --> new Child

All can be created using one form.

Additionally, I also want to implement the following process:

new Application --> existing Submitter --> new Child

The existing object should be chosen by a dropdown list box.

Here is the (simplified, working) code of the view:

new.html.erb

<%= simple_form_for(@application)  do |f| %>
    <%= f.simple_fields_for :submitter do |submitter| %>  
        <%= render "submitter_fields", :f => submitter %>
    <% end %>
<% end %>

_submitter_fields.html.erb

<%= f.input :firstname %>
<%= f.input :lastname %>
<%= render "child", :f => f %>

_child.html.erb

<div id="childs">
    <%= f.simple_fields_for :children do |child| %>
      <%= render "child_fields", :f => child %>
    <% end %>
    <div class="links">
        <%= link_to_add_association 'Add child', f, :children %>
    </div>
</div>

_child_fields.html.erb

<div class="nested-fields">
    <%= f.input :firstname %>
    <%= f.input :lastname %>
    <%= link_to_remove_association "Remove child", f %>
</div>

Now I want to add a dropdown list which is populated with all existing Submitters. For example:

<%= f.assosciation :submitter %>

And here starts my problem: To build the form for adding a new child to the selected submitter, I need to assign this object to the form builder. I have no idea how to do this.

Can somebody give me a hint how to implement this? Or is this scenario simply not possible?

Thanks in advance!

Christian

Answer 1

simple_fields_for takes a second argument the object: https://github.com/plataformatec/simple_form/blob/master/lib/simple_form/action_view_extensions/form_helper.rb#L33 maybe if you pass your existing submitter it will work.