please help solve the problem.

i create scaffold Product, fill it, and try export product data to csv-format file.
application\_controller.rb:

```
class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception
  require 'csv'
end

```

product controller:

```
class ProductsController < ApplicationController
  def index
    @products = Product.all

    respond_to do |format|
      format.html
      format.csv do
        headers['Content-Disposition'] = "attachment; filename=\"user-list\""
        headers['Content-Type'] ||= 'text/csv'
      end
    end    
  end
end

```

app/views/users/index.csv.erb:

```
<%- headers = [
  'title', 
  'is_catalog', 
  'parent_id', 
  'lft', 
  'rgt', 
  'description'
] -%>
<%= CSV.generate_line headers %>
<%- @products.each do |product| -%>
  <%= CSV.generate_line([
    product.title, 
    product.is_catalog, 
    product.parent_id, 
    product.lft, 
    product.rgt, 
    product.description
  ]) %>
<%- end -%>

```

schema:

```
create_table "products", force: :cascade do |t|
  t.string   "title"
  t.text     "description"
  t.boolean  "is_catalog"
  t.integer  "parent_id"
  t.integer  "lft"
  t.integer  "rgt"
end

```

but after open link 'host/products.csv', downloaded csv-file which contain '###' symbols in 'lft' column. see it on screenshot <http://hostingkartinok.com/show-image.php?id=f08a98e485285e4adb23f5c148620aa2> 

please help export 'lft' column values