Payday is a Ruby gem that will help you create simple invoices. It’s a generic PDF invoicing library and as I will show you in this tutorial, it can be easily used to help you create invoices from Paypal transactions.

First thing to do, add the gem to your Gemfile :

gem "payday"

Next, you can create a rails initializer file with your company infos :

# /config/initializers/payday.rb
Payday::Config.default.invoice_logo = "#{Rails.root}/public/images/logo.png"
Payday::Config.default.company_name = "My Company inc."
Payday::Config.default.company_details = "100 Sunset Blvd\nHollywood\nUnited States\ninfo@mycompany.com"

When a client makes a purchase on Paypal, you can configure your account to receive Instant Payment Notifications (IPN). I save each transaction in a Payment model and dump the paypal IPN request params in a serialized hash called paypal_params. This is the method from my model class I use to generate the invoice :

# app/models/payment.rb
serialize :paypal_params

def generate_pdf_invoice
  invoice = Payday::Invoice.new(
    :invoice_number => paypal_params['invoice'],
    :currency => paypal_params['mc_currency'])
  invoice.paid_at = invoice.due_at = created_at.to_date
  invoice.bill_to = invoice.ship_to = paypal_params.slice(
    'address_name', 'address_street', 'address_city',
    'address_zip', 'address_country').values.join("\n")
  invoice.line_items << Payday::LineItem.new(
    :price => paypal_params['mc_gross'],
    :quantity => 1,
    :description => paypal_params['item_name'])
  invoice.notes = "Thank you for your purchase!"
  invoice.render_pdf
end

Obviously, you will want to adjust this code to fit what you are selling. In my case, there is always only one line item in my transactions.

Finally, I make the invoice downloadable from the user account page. The controller method works like this :

# app/controllers/payments_controller.rb
def pdf_invoice
  payment = Payment.find_by_tx_id! params[:id]
  respond_to do |format|
    format.pdf do
      send_data payment.generate_pdf_invoice,
        :filename => payment.invoice_filename,
        :type => "application/pdf"  , :disposition => "inline"
    end
  end
end

Again, you will probably have to adjust this method for your own needs. Don’t forget to add the pdf mime type to the mime_types.rb initializer :

# /config/initializers/mime_types.rb
Mime::Type.register 'application/pdf', :pdf

There’s a lot more you can do with Payday. It supports I18n and it integrates well with ActiveRecord. I encourage you to take a look at the readme on github.

1. Prepare the map in your model

In your Geolocation model, start by adding this snippet of code which will initialize your map.

def map
  @map ||= prepare_map
end

def mapped?
  latitude && longitude
end

def coordinates
  [latitude, longitude]
end

private

def prepare_map
  return unless mapped?
  returning GMap.new("gmap") do |map|
    map.control_init(:large_map => true, :map_type => true)
    map.center_zoom_init(coordinates, 15) # Set the center and zoo level
    map.overlay_init(GMarker.new(coordinates))
  end
end

The important method here is prepare_map. What it does is create a new map centered at the given coordinates. The overlay_init method sets a marker at the coordinates position. This is a basic vanilla map initialization. You might want to read the YM4R api for more options like adding an info window or multiple markers.

2. Call it from your controller

In our controller, we will set the @map variable to make it accessible in our view :

@map = customer.geolocation.map

3. Display the map in your view

You will need this snippet of code in the header section of your document to do the proper javascript imports and initializations :

= GMap.header
= @map.to_html

And in the body of your view, where you want to display the map, simply add :

@map.div(:width => 600, :height => 400)

This last line will generate a div with the id “gmap” (or whatever name you set in the GMap.new function). I find it’s cleaner to just set the width an height through CSS.

4. Adding complexity

This technique will only work if you display only one map on the page. The map needs to be visible on page load to be properly displayed. But what if there is multiple maps you want to display on the same page? And what if you want to show them in overlay popups? You probably don’t want to initialize them all on page load since it will freeze the client browser. This will require some javscript hacking. I will show you how to do that next week!