Saving an associated polymorphic object duplicates it

Question

I have two models, one of them being polymorphic and second one being a "parent" one:

class Person
  has_one :asset, as: :assetable
  accepts_nested_attributes_for :asset
end

class Asset
  belongs_to :assetable, class_name: Asset.name, polymorphic: true
end

And after saving a following form:

<% form_with model: @person do |f| %>
  <% f.fields_for :asset do |ff| %>
    <%= ff.text_field :name %>
  <% end %>
<% end %>

The associated Asset object is not being updated but, instead, a new copy of Asset is being created with given name and is being reassigned to the Person object. Why is that happening and how can i make that properly?

I'm on Rails 7.1.3 and Asset uses STI if that changes anything.

Actually, you are missing the associated asset details in the fields_for. guides.rubyonrails.org/form_helpers.html#the-fields-for-helper <% f.fields_for :asset, @person.asset do |ff| %> — Thang
– Thang, Commented Jul 11, 2024 at 9:00

GProst · Accepted Answer · 2024-07-11 09:22:30Z

1

You should set update_only: true parameter for accepts_nested_attributes_for declaration:

accepts_nested_attributes_for :asset, update_only: true

Otherwise since you don't pass asset's ID in the form it creates a new one instead of updating the already existing one.

answered Jul 11, 2024 at 9:22

GProst

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1 Comment

mbajur Over a year ago

Thank you! I temporarily resolved it by allowing id in permitted params which was far from ideal but i never head of that update_only setting and now it works like charm. Thank you! :)

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