Recipe 16.8. Charging a Credit Card

Problem

You want to charge a credit card from within your Ruby application.

Solution

To charge credit cards online, you need an account with a credit card merchant. Although there are many to choose from, Authorize.Net is one of the best and most widely used. The payment library encapsulates the logic of making a credit card payments with Authorize.Net, and soon it will support other gateways as well. It's available as the payment gem.

require 'rubygems'
	require 'payment/authorize_net'
	
	transaction = Payment::AuthorizeNet.new(
	  :login           => 'username',
	  :transaction_key => 'my_key',
	  :amount          => '49.95',
	  :card_number     => '4012888818888',
	  :expiration      => '0310',
	  :first_name      => 'John',
	  :last_name       => 'Doe'
	)

The submit method sends a payment request. If there's a problem with your payment (probably due to an invalid credit card), the submit method will raise a Payment::PaymentError:

begin
	  transaction.submit
	  puts "Card processed successfully: #{transaction.authorization}"
	rescue Payment::PaymentError
	  puts "Card was rejected: #{transaction.error_message}"
	end
	# Card was rejected: The merchant login ID or password is invalid
	# or the account is inactive.

Discussion

Some of the information sent during initialization of the Payment::AuthorizeNet class represent your account with Authorize.Net, and will never change (at least, not for the lifetime of the account). You can store this information in a YAML file called .payment.yml in your home directory, and have the payment library load it automatically. A .payment.yml file might look like this:

login: username
	transaction_key: my_key

That way you don't have to hardcode login and transaction_key within your Ruby code.

If you're using the payment library from within a Rails application, you might want to put your YAML hash in the config directory with other configuration files, instead of in your home directory. You can override the location for the defaults file by specifying the :prefs key while initializing the object:

payment =  
Payment::AuthorizeNet
	    .new(:prefs => "#/config/payment.yml")
	payment.amount = 20
	payment.card_number = 'bogus'
	payment.submit rescue "That didn't work"

Notice that after the Payment::AuthorizeNet object has been initialized , you can change its configuration with accessor methods .

Like most online merchants, Authorize.Net uses its own XML-formatted responses to do transactions over HTTPS. Some merchants , such as Payflow Pro, use proprietary interfaces to their backend that require a bridge with their Java or C libraries. If you're using Ruby, this approach can be cumbersome and difficult. It's worth investing some time into researching how flexible the backend is before you decide on a merchant platform for your Ruby application.

See Also

• Recipe 2.17, "Checking a Credit Card Checksum"

• The online RDoc for the payment library (http://payment. rubyforge .org/)

• http://authorize.net/