Why Don't my Parameters get Passed in Ruby on Rails?

Question

So, I'm really new to Ruby on Rails and the whole thing still sounds like Chinese to me. Excuse me if this is a stupid question, but I'm trying to make a new button on my app that lets me copy things.

On my form I have:

%span.btn.btn-mini.btn-inverse= link_to copy_image, copy_campaign_signal_processor_item_path(@campaign, @processor, item) ,data: { toggle:"modal",target: "#myModal"}, remote: true

That works fine and creates the button for me. Then, in routes.rb, I have:

resources :signal_processors, exclude: [:index, :new, :create], controller: 'processors' do

        member do
          get :modify, :action => :edit, :force_schema_update => true
        end

        resources :items do
          member do
            get :copy
          end
        end

Finally, in the items_controller.rb, I have:

  def copy
    @overlay_title = "Copy #{@processor.item_name}"
    @processor.properties.each do |property|
      unless @item.property_values.collect{|a| a.property_id}.index(property.id)
        @item.property_values << SignalProcessor::PropertyValue.new(property: property)
      end
    end

    respond_to do |format|
      format.js
    end
  end

The problem is that for some reason item doesn't seem to get passed to the copy function in items_controller.rb, so every time I click the copy button, I get the error:

undefined method property_values' for nil:NilClass`

for the line:

unless @item.property_values.collect{|a| a.property_id}.index(property.id)

What am I doing wrong? Why isn't item getting passed?

Answer 1

@item is an instance variable, and its value is nil unless you set otherwise. It's what we have here - you don't set @item anywhere in this action, which is why it's nil . You should probably (assuming you have corresponding Item model) type:

@item = Item.find(params[:id])

before you'd like to use @item value.

Answer 2

First, you need to amend your form view to pass the Item id, which you can use to look up the corresponding model object in your controller:

%span.btn.btn-mini.btn-inverse= link_to copy_image, copy_campaign_signal_processor_item_path(@campaign, @processor, item.id) ,data: { toggle:"modal",target: "#myModal"}, remote: true

In your form, you're passing three arguments to your path, but you haven't named them in your route yet. You can name the parameters you'll be passing to the copy route within the :items resource block:

resources :items do
    member do
        get 'copy/:campaign/:processor/:item_id', :action => 'copy'
    end
end

Then, in your controller, you can look up your Item by ID:

def copy
   @item = Item.find(params[:item_id])
   ...
end