Question

Rails 3.2.12 and Ruby 1.9.3 and Haml

I would like to use the count of attribute to control the display of a ‘link_to “remove”‘, but I am having problems with setting up the logic.

Following is some code from my form as it is currently:

    .field
      = codeline.label :name, "Units Alloc"
      %br/
      = codeline.text_field :units_alloc, :precision => 6, :scale => 2, :size => 10,
       :class => "ui-state-default"
      = codeline.hidden_field :_destroy
      = link_to "remove", '#', class: "remove_fields"

this works well but I have the ‘remove’ link showing up and I would prefer it to only show if there are two :units_alloc attributes.

This is what I tried:

    .field
      = codeline.label :name, "Units Alloc"
      %br/
      = codeline.text_field :units_alloc, :precision => 6, :scale => 2, :size => 10,
       :class => "ui-state-default"
      - if :units_alloc.count > 1
      = codeline.hidden_field :_destroy
      = link_to "remove", '#', class: "remove_fields"

and here is my error:

       NoMethodError in Contracts#new

       Showing /home/tom/rails_projects/tracking/app/views/contracts
       /_codeline_fields.html.haml where line #9 raised:

       undefined method `count' for :units_alloc:Symbol

if I use units_alloc in the argument instead of the symbol, I still get an error:

        NameError in Contracts#new

        Showing /home/tom/rails_projects/tracking/app/views/contracts
        /_codeline_fields.html.haml where line #9 raised:

        undefined local variable or method `units_alloc' for
        #<#<Class:0xadbde90>:0xa8956e8>

I tried to use ‘codeline.units_alloc’ but this did not work and the same error was flagged.

Any suggestions, or pointers to help me resolve this issue?

Thanks.

Solution: Thanks to James Scott Jr.

app/controller/contracts_controller.rb

  def New
     @show_remove = false
     ....
     ....
   end

app/views/contracts/_codelines_fields.html.haml

   .field
      = codeline.label :name, "Units Alloc"
      %br/
      = codeline.text_field :units_alloc, :precision => 6, :scale => 2, :size => 10,
       :class => "ui-state-default"
      - if @show_remove
          = codeline.hidden_field :_destroy
          = link_to "remove", '#', class: "remove_fields"
      - else
         - @show_remove = true

And that did it … the remove button only shows in the second and subsequent row of attributes.

Answer 1

By the time you’re in the form (partial), codeline doesn’t refer to an instance the instance of Codeline that the form (partial) is for, but an instance of an ActionView::Helpers::FormBuilder that simple knows how to associate information the the instance of Codeline. You knew that because in the first line of the partial, you have codeline.object.build_code.

So, if you want to access the information about the units_alloc associated, you would access them with codeline.object.units_alloc. That will give you your data for your conditional.