How to Upload a Text File and Parse Contents into Database in Ror

Parsing a textfile in Ruby on Rails w/o saving it

When you upload a file, Rails will create a file in the tmp directory, which will later be deleted automatically. Therefore, you don't have to do anything for the upload to be automatically deleted. That means that if you wanted to keep the file, you would need to copy it manually to a permanent location.

You can access the temporary file by calling the tempfile method on params[:file_upload], for example:

class UploadController < ApplicationController
  def new
    # upload form
  end

  def create
    data = params[:file_upload].tempfile.read
    parts = data.split(">>>>\n")

    # do something with parts
  end
end

Rails - Reading uploaded text file

You should add multipart to your form just like the following

<%= form_tag '/greetings/hello', multipart: true do %>

Import CSV files into SQL database in ROR

Your rake task looks more like a regular ruby script than a rake task. If you want to use rake for this, try something like:

require 'csv'

namespace :import do
  desc 'Imports csv data into db'
  task from_csv: :environment do
    csv_text = File.read('/Path/to/csv/Item.csv')
    csv = CSV.parse(csv_text, :headers => true)
    csv.each do |row|
      Item.create!(row.to_hash)
    end
  end
end

and invoke it with rake import:from_csv

Uploading a txt file without saving it to database using ajax

If you want to upload file with AJAX and rails forms you can use remotipart gem:

Remotipart is a Ruby on Rails gem enabling AJAX file uploads with
jQuery in Rails 3.0 and Rails 3.1 remote forms. This gem augments the
native Rails jQuery remote form functionality enabling asynchronous
file uploads with little to no modification to your application.

For me it works with Rails 3.2 as well.

https://github.com/JangoSteve/remotipart

http://rubygems.org/gems/remotipart

how to read a User uploaded file, without saving it to the database

You are very close. Check the class type of params[:uploaded_file], it should typically be either a StringIO or a Tempfile object -- both of which already act as files, and can be read using their respective read method(s).

Just to be sure (the class type of params[:uploaded_file] may vary depending on whether you are using Mongrel, Passenger, Webrick etc.) you can do a slightly more exhaustive attempt:

# Note: use form validation to ensure that
#  params[:uploaded_file] is not null

file_data = params[:uploaded_file]
if file_data.respond_to?(:read)
  xml_contents = file_data.read
elsif file_data.respond_to?(:path)
  xml_contents = File.read(file_data.path)
else
  logger.error "Bad file_data: #{file_data.class.name}: #{file_data.inspect}"
end

If, in your case, it turns out that params[:uploaded_file] is a hash, make sure that you have not mistakingly flipped the object_name and method parameters when invoking file_field in your view, or that your server is not giving you a hash with keys like :content_type etc. (in which case please comment on this post with the Bad file_data ... output from development.log/production.log.)

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