Upload files with Ruby/Sinatra

Uploading files with Ruby/Sinatra

REQUIRED GEMS

- Sinatra

- HAML

THE VIEW

Let’s start by setting up our form (using HAML, because that’s what the cool kids are using):

File: views/upload.haml:

%html

  %body

    %h1 File uploader!

    %form(method="post" enctype='multipart/form-data')   

      %input(type='file' name='myfile')    

      %br

      %input(type='submit' value='Upload!')

Nothing fancy, but it’ll do for now.

REQUEST HANDLING

Now, let’s make our server handle the GET- and POST-requests coming from the client:

File: server.rb:

require 'rubygems'

require 'sinatra'

require 'haml'

# Handle GET-request (Show the upload form)

get "/upload" do

  haml :upload

end      

    

# Handle POST-request (Receive and save the uploaded file)

post "/upload" do 

  File.open('uploads/' + params['myfile'][:filename], "w") do |f|

    f.write(params['myfile'][:tempfile].read)

  end

  return "The file was successfully uploaded!"

end

As you can see, you don’t have to write much code to get this to work. The params-hash contains our uploaded element with data such as filename, type and the actual datafile, which can be accessed as a Tempfile-object. We read the contents from this file and store it into a directory called uploads, which you will have to create before running this script.

Here’s an example of what the params-hash may look like when uploading a picture of a cat:

{

  "myfile" => {

    :type => "image/png",

    :head =>  "Content-Disposition: form-data;

               name=\"myfile\";

               filename=\"cat.png\"\r\n

               Content-Type: image/png\r\n",

    :name => "myfile",

    :tempfile => #<File:/var/folders/3n/3asd/-Tmp-/RackMultipart201-1476-nfw2-0>,

    :filename=>"cat.png"

  }

}