Undefined method `customer_name' in nested association in Rails

Question

I'm pretty new in Rails and I need your help. I have Job model, Invoice model and Item model.

job.rb model have - has_one :invoice, dependent: :destroy accepts_nested_attributes_for :invoice

invoice.rb have - belongs_to :job, optional: true, :foreign_key => 'job_id' has_many :items, dependent: :destroy accepts_nested_attributes_for :items

item.rb have - belongs_to :invoice, optional: true, :foreign_key => 'invoice_id'

Everything is ok, it creating the job and invoice with items inside and on invoice show it generate the invoice but in invoices/index I want to list all invoices in a table but I can't get = @invoice.job.customer_name.capitalize it give me a error - NoMethodError in Invoices#index undefined method `customer_name' for nil:NilClass.

It is like job is nil. My question is why in invoices/show.html.erb I can access
= @invoice.job.customer_name.capitalize and in index it give me error ?

As you can see in invoices/show.html.haml I have = @invoice.job.customer_name.capitalize and it give me correct data:

.container.invoice
  .row
    .col-sm-6
      - if  current_user.logo.present? 
        = image_tag current_user.logo.url(:thumb) 
      - else 
        = image_tag 'blank.jpg'
    .col-sm-3
    .col-sm-3
      %h3
        = current_user.full_name.titleize
      %p  
      = current_user.email
      %p
      = current_user.phone
  %hr
  .row
    .col-sm-6
      %h4
        Customer :
        = @invoice.job.customer_name.capitalize.html_safe
      %p
      %b
        Phone: 
      = @invoice.job.customer_tel
      %p
      %b
        Email:
      = @invoice.job.customer_email
    .col-sm-3
    .col-sm-3
      %p
      %b
        Invoice: #  
      = @invoice.id
      %p
      %b
        Date:
      = @invoice.created_at.strftime("%B %d, %Y")
  %hr
  .row
    .col-sm-12
      %table.table.table-striped.table-hover
        %thead
          %tr.sortable-table
            %th.col-sm-1
              Item Id
            %th.col-sm-3
              Item/Operation
            %th.col-sm-3
              Unit cost/Hr rate
            %th.col-sm-3
              Qty
            %th.col-sm-2
            %th.col-sm-3
              Amount
        %tbody
        
        - @invoice.items.each do |item|
          %tr.sortable-table
            %th
              = item.id
            %th
              = item.name 
            %th
              = number_to_currency item.unit_cost 
            %th
              = item.qty
            %th 
            %th
              - amount = number_to_currency(item.unit_cost * item.qty) 
              = amount
            
  %hr
  .row
    .col-sm-6
    .col-sm-3
    .col-sm-3
      %b
        Subtotal
        - sum = 0
        - @invoice.items.each do |item|
          - if item.qty?
            - subtotal = (item.unit_cost * item.qty)
            - sum += subtotal
        = number_to_currency(sum)  
      %p
      %b  
        Tax
        = number_to_currency(sum * (@invoice.tax/100))
      %p  
      %h4
        %b
          Total
          = number_to_currency((sum * (@invoice.tax/100)) + sum)
  %hr

= link_to 'Edit', edit_invoice_path(@invoice)
\|
= link_to 'Back', invoices_path

But in invoices/_invoice.html.erb I have the error :

%h1 Listing invoices

%table.table.table-striped.table-hover
  %thead
    %tr.sortable-table
      %th
        Id
      %th
        Job Id
      %th
        Item
      %th
        Unit cost
      %th
        Qty
      %th
        Amount
  %tbody
    = render @invoices
%br

= link_to 'New Invoice', new_invoice_path

<tr>
  <td>
    <%= invoice.id %>
  </td>
  <td>
    <%= invoice.job_id %>
  </td>
  <td>

  </td>
  <td>
    <%= invoice.unit_cost %>
  </td>
  <td>
    <%= invoice.qty %>
  </td>
  <td>
    <%= invoice.job.customer_name %>
  </td>
  <td>
    <%= link_to 'Details', invoice, class: 'btn btn-primary btn-xs' %>
  </td>
  <td>
    <%= link_to "", edit_invoice_path(invoice), id: "edit_#{invoice.id}", class: 'glyphicon glyphicon-pencil index-icons' %>
  </td>
  <td>
    
     <%= link_to "", invoice_path(invoice), method: :delete, id: "delete_invoice_#{invoice.id}_from_index", class: 'glyphicon glyphicon-trash index-icons', data: {confirm: 'Are you sure ?'} %>
  </td>
</tr>

Thank you, and if you need more code let me know.

Update:

[you see invoice Id 47 have job id  67][1]
[the job id 67 is exist][2]
[on the invoice show  I have name of customer][3]


  [1]: https://i.sstatic.net/ODAkb.png
  [2]: https://i.sstatic.net/uGK21.png
  [3]: https://i.sstatic.net/sRTWS.png

Answer 1

NoMethodError in Invoices#index undefined method `customer_name' for nil:NilClass.

This means where you are calling customer_name:

@invoice.job.customer_name.capitalize.html_safe

You are calling it on nil, or in other words:

@invoice.job

returns nil. If the invoice does not have a job associated with it, any methods involving the invoice's job will fail (apart from just @invoice.job, which will return nil).

Your two options are to either make sure every invoice has a job associated with it before rendering, or to rewrite your view template as:

.container.invoice
  .row
    .col-sm-6
      - if  current_user.logo.present? 
        = image_tag current_user.logo.url(:thumb) 
      - else 
        = image_tag 'blank.jpg'
    .col-sm-3
    .col-sm-3
      %h3
        = current_user.full_name.titleize
      %p  
      = current_user.email
      %p
      = current_user.phone
  %hr
  .row
    .col-sm-6
      - if @invoice.job
        %h4
          Customer :
          = @invoice.job.customer_name.capitalize.html_safe
        %p
        %b
          Phone: 
        = @invoice.job.customer_tel
        %p
        %b
          Email:
        = @invoice.job.customer_email
      .col-sm-3
      .col-sm-3
        %p
        %b
          Invoice: #  
        = @invoice.id
        %p
        %b

This will only display the bottom section of the view if a job is associated with the @invoice