gistfile1.txt

<h1>Editing coupon</h1>
<%= form_for(@coupon, :html => {:multipart => true}) do |f| %>
<% if @coupon.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@coupon.errors.count, "error") %> prohibited this coupon from being saved:</h2>

      <ul>
      <% @coupon.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :name %><br />
    <%= f.text_field :name %>
  </div>
  <div class="field">
    <%= f.label :price %><br />
    <%= f.text_field :price %>
  </div>
  <div class="field">
    <%= f.label :description %><br />
    <%= f.text_field :description %>
  </div>
  <div class="field">
    <%= f.label :data %>
    <%= f.file_field :data %>
  </div>
  <div class="field">
    <%= f.label :datalogo %>
    <%= f.file_field :datalogo %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>


<%= link_to 'Show', @coupon %> |
<%= link_to 'Back', coupons_path %>
>>>>>>>>>>>>>
controller:

def update
    
    @coupon = Coupon.find(params[:id])
    @coupon.mime_type=params[:coupon][:data].content_type
    @coupon.filename  = params[:coupon][:data].original_filename
    @coupon.data= params[:coupon][:data].read

    @coupon.mime_typelogo=params[:coupon][:datalogo].content_type
    @coupon.filenamelogo  = params[:coupon][:datalogo].original_filename
    @coupon.datalogo= params[:coupon][:datalogo].read 

    respond_to do |format|
      if @coupon.update_attributes(params[:coupon])
        format.html { redirect_to @coupon, notice: 'Coupon was successfully updated.' }
        format.json { head :no_content }
      else
        format.html { render action: "edit" }
        format.json { render json: @coupon.errors, status: :unprocessable_entity }
      end
    end
  end
>>>>>>>>>>>>>>>>>>>>>>>>>>
Error:
 NoMethodError in CouponsController#update

undefined method `name' for nil:NilClass

Rails.root: C:/Users/shruti.k/Desktop/ror/couponsys v2
Application Trace | Framework Trace | Full Trace

app/controllers/coupons_controller.rb:79:in `block in update'
app/controllers/coupons_controller.rb:78:in `update'

Request

Parameters:

{"utf8"=>"✓",
 "_method"=>"put",
 "authenticity_token"=>"g4T5is35CjQ2h8U1CDFClVIQYfBevNUMblytIvEwIOY=",
 "coupon"=>{"name"=>"Shopper Stop",
 "price"=>"20.0",
 "description"=>"5% discount on a bill of more than 1000/-",
 "data"=>#<ActionDispatch::Http::UploadedFile:0x299d168 @original_filename="coupon7.jpg",
 @content_type="image/jpeg",
 @headers="Content-Disposition: form-data; name=\"coupon[data]\"; filename=\"coupon7.jpg\"\r\nContent-Type: image/jpeg\r\n",
 @tempfile=#<File:C:/Users/shruti.k/AppData/Local/Temp/RackMultipart20130805-3780-12leu9m>>,
 "datalogo"=>#<ActionDispatch::Http::UploadedFile:0x299cf10 @original_filename="logo1.jpg",
 @content_type="image/jpeg",
 @headers="Content-Disposition: form-data; name=\"coupon[datalogo]\"; filename=\"logo1.jpg\"\r\nContent-Type: image/jpeg\r\n",
 @tempfile=#<File:C:/Users/shruti.k/AppData/Local/Temp/RackMultipart20130805-3780-n4qv0r>>},
 "commit"=>"Update Coupon",
 "id"=>"9"}

Its working perfectly now.:)