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• Table of contents
• Document Scaffold
  • Showing the Document
  • File Size Validation
• Resources

This is a simple guide for setting up a simple file upload to database with Ruby on Rails.

• Create the new Ruby on Rails web application:
  

  rails new uploadr
  

• Change into the message_app directory:
  

  cd uploadr
  

• Start the rails development web server locally:
  

  bundle exec rails s
  

  • NOTE: The development web server bind the IP address to the localhost by default, so accessing it over the network will not work. To allow network access to the development web server:
    

    bundle exec rails s -b 0.0.0.0
    

Document Scaffold¶

• Generate the scaffold model, view, and controller code for the document.
  

  bundle exec rails generate scaffold document filename:string content_type:string file_contents:binary
  

• Edit the route config:
  

  vi config/routes.rb
  

  • And add the default route to the app:
    

    Uploadr::Application.routes.draw do
      resources :documents
      root :to => 'documents#index'
    end
    

• Edit the form view:
  

  vi app/view/documents/_form.html.erb
  

  • And remove the unneeded form div tags, leaving the following:
    

      <div class="field">
        <%= f.file_field :file %>
      </div>
      <div class="actions">
        <%= f.submit %>
      </div>
    

• Edit the document controller:
  

  vi app/controllers/documents_controller.rb
  

  • And the following right b+efore the final end+ statement to allow file as a parameter so you can use it in the model:
    

    def document_params
      params.require(:document).permit(:file)
    end
    

• Next edit the document model:
  

  vi app/models/document.rb
  

  • And add the following to update the model to read and save the file
    

      def initialize(params = {})
        file = params.delete(:file)
        super
        if file
          self.filename = sanitize_filename(file.original_filename)
          self.content_type = file.content_type
          self.file_contents = file.read
        end
      end
    
      private
      def sanitize_filename(filename)
        return File.basename(filename)
      end
    

Showing the Document¶

• Edit the document controller again:
  

  vi app/controllers/documents_controller.rb
  

  • And modify the show method to send the raw file for viewing:
    

    def show
      send_data(@document.file_contents,
                type: @document.content_type,
                filename: @document.filename)
    end
    

File Size Validation¶

• Edit the document model again:
  

  vi app/controllers/documents_controller.rb
  

  • And modify the file using the following code:
    

    validate :max_file_size
    
    def initialize(params = {})
      # File is now an instance variable so it can be validated.
      @file = params.delete(:file)
      super
      if @file
        self.filename = sanitize_filename(@file.original_filename)
        self.content_type = @file.content_type
        self.file_contents = @file.read
      end
    end
    
    NUM_BYTES = 1048576 # 1MB
    def max_file_size
      if (@file.size.to_f / NUM_BYTES) > 1
        errors.add(:file, 'File size cannot be over #{NUM_BYTES} bytes.')
      end
    end
    

Resources¶

• http://ryan.endacott.me/2014/06/10/rails-file-upload.html
• https://matt.berther.io/2007/10/19/uploading-files-to-a-database-using-rails/
• https://www.tutorialspoint.com/ruby-on-rails/rails-file-uploading.htm
• https://gist.github.com/macek/610596