Ruby on Rails

On Saturday, January 20, 2018 at 3:54:27 AM UTC, kenatsun wrote:
> Using scaffold, I generated two models, Person and Offer, and the forms to manage them.  Offer has a belong_to association with Person.  After running the generator, all the forms immediately worked fine. 
>
> But then I discovered an external requirement that the foreign key column in the offers table, which was named person_id per Rails conventions, needed to be renamed as worker_id.  Since then, the Offer forms don't work.  They evoke a variety of errors, all related to the renamed column.  It seems that the system no longer recognizes it as implementing the Offer to Person association.
>

You need to tell the has_many/belongs_to associations to use the new key, ie

(In Offer)

belongs_to :person, foreign_key: "worker_id"

And similarly for the has_many in the Person class. The form helpers need to be using the worker_id , since person_id doesn't exist anymore.

Fred







> I figure I need to make some declaration somewhere to restore this associative functionality, but I can't figure out how to do this.  Can you help?
>
> Here are some details:
>
> The generate commands I used were:
>
>
> rails generate scaffold Person name:string
> rails generate scaffold Offer terms:string person:belongs_to
> rake db:migrate
>
> I tweaked the Offer forms a bit to show People's names in display pages and provide a drop-down on edit forms.  The tweaked Offer index.html.erb looked like this:
>
>
>
> ...
>    <% @offers.each do |offer| %>
>       <tr>
>         <td><%= offer.terms %></td>
>         <td><%= offer.person.name %></td>
>         <td><%= link_to 'Show', offer %></td>
>         <td><%= link_to 'Edit', edit_offer_path(offer) %></td>
>         <td><%= link_to 'Destroy', offer, method: :delete, data: { confirm: 'Are you sure?' } %></td>
>       </tr>
>     <% end %>
> ...and the tweaked Offer _form.html.erb looked like this:
>
>
> <%= form_with(model: offer, local: true) do |form| %>
> ...
>   <div class="field">
>     <%= form.label :terms %>
>     <%= form.text_field :terms, id: :offer_terms %>
>   </div>
>
>   <div class="field">
>     <%= form.label :person_id %>
>     <%= form.collection_select :person_id, Person.order(:name), :id, :name %>
>   </div>
> ...
>
> At this point, everything worked fine. 
>
> Then I wrote and executed this migration:
>
>
> class RenameOfferPersonId < ActiveRecord::Migration[5.1]
>   def change
>       rename_column :offers :person_id :worker_id
>   end
> end
> Since then, all of my Offer forms get errors, always related to the renamed foreign key column.  Here's the error for index.html.erb:
>
>
>
>
> Showing /home/ec2-user/environment/ww1/app/views/offers/index.html.erb where line #18 raised:
>
> undefined method `name' for nil:NilClass
> ...
>         <td><%= offer.person.name %></td>
>
> If I change the offending line to:
>
>
>         <td><%= offer.worker_id %></td>
> the page displays, but only the value of worker_id is displayed, not the name of the referenced Person.
>
> The Offer edit form displays, including its dropdown box containing Person names.  But when I try to save an update, I get:
>
>
> ActiveModel::UnknownAttributeError in OffersController#update
> unknown attribute 'person_id' for Offer.
>
>
> Extracted source (around line #44):
>
> ...
>
>
>
>
> 44 if @offer.update(offer_params)
>
> If I change these lines in _form.html.erb
>
>
>     <%= form.label :person_id %>
>     <%= form.collection_select :person_id, Person.order(:name), :id, :name %>
> to
>
>
>     <%= form.label :worker_id %>
>     <%= form.collection_select :worker_id, Person.order(:name), :id, :name %>
> the form still displays OK, but when I try to save an update, I get a different error:
>
>
>
> 1 error prohibited this offer from being saved:Person must exist
>
> ~ Thanks in advance for your help
> ~ Ken

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