error message when uploading file in ruby on rails

Question

The file uploading is working properly using ruby on rails. Now i need to validate my uploading. It should validate and display error message when no file is selected after clicking upload. Please help me with a code for this error validation.

My view file is (uploadfile.html.erb):

     <h1>File Upload</h1>
     <%= form_tag({action: :uploadFile}, multipart: true) do %>
     <p><label for="upload_file">Select File</label>
     <%= error_messages_for :data_file %>
     <%= file_field 'upload', 'datafile' %></p>
     <%= submit_tag "Upload" %>
     <%end%>

My controller file is (upload_controller.rb):

    class UploadController < ApplicationController
    def uploadFile
    post = DataFile.save(params[:upload])
    render :text => "File has been uploaded successfully"
    end
    end

My model file is (data_file.rb):

    class DataFile < ActiveRecord::Base
    attr_accessor :upload
    validates_attachment_presence :upload unless :upload
    def self.save(upload)
    name =  upload['datafile'].original_filename
    directory = "public/data"
    # create the file path
    path = File.join(directory, name)
    # write the file
    File.open(path, "wb") { |f| f.write(upload['datafile'].read) }
    end
    end

if in case you want to handle in controller action use if params[:upload].present? and params[:upload][:datafile].present? — Nithin
– Nithin, Commented Apr 8, 2014 at 11:03
@Nithin i need to show alert message like "no file chosen please choose file" after clicking upload — user3279260
– user3279260, Commented Apr 8, 2014 at 12:12

Pavan · Accepted Answer · 2014-04-08 10:58:18Z

1

If you are using paperclip gem,you can do like this in your Model.

validates_attachment_presence :datafile unless :datafile

It checks the existence of uploaded file.

Update

For displaying the error messages,just add this line to your form

<%= error_messages_for :upload_file %> #Assuming your model name is `upload_file`

edited Apr 8, 2014 at 10:58

answered Apr 8, 2014 at 10:36

Pavan

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15 Comments

user3279260 Over a year ago

everything good.but i need the error message should be displayed when no file is chosen.

user3279260 Over a year ago

i'm getting this error " undefined method `error_messages_for' for #<#<Class:0x3217050>:0x2a9b1f0> "

user3279260 Over a year ago

i posted my full coding

Pavan Over a year ago

@user3279260 Try moving this line <%= error_messages_for :data_file %> just below the form_tag line

Pavan Over a year ago

@user3279260 Now i get it.Its because you added the validation in the wrong model.it should be in Upload model.

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