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see also coding/checkout


The checkout subsystem handles customer interaction from the point when the customer presses "check out" on the shopping cart up to the point where the order is placed ("finish" button in old system).


  • Record shipping information
  • Record payment information
    • Allow customer to indicate that payment address is same as shipping.
  • Prevent customer from proceeding if required fields are missing or contain invalid data.
  • Keep records of customer information as entered and also as interpreted for order processing.
  • Send notification email to customer and store when order is placed.
    • Present customer with printable/saveable receipt.



Converting the cart data to order data seems to be one of the trickiest parts to get right.

Basically, the Cart object now supervises the creation of new records as needed. Customer objects just create customer records, not address or name or whatever.


We'll treat the shopping cart as being Page 0 of the checkout process, even though it's handled by a different page class, because it is part of the checkout navigation flow i.e. from Page 1, the "back" button takes you back to the shopping cart page.

It looks like the best way to handle form navigation is to have constant control names for the "back" and "next" buttons and to include the name of the submitting form in a hidden field.[1]

Where form data does not need to be saved, switching modes for a given page can be done with a clickable link rather than a button.

  • page 0: shopping cart - handled by a different Page class, but can be navigated to from here (i.e. pressing the "back" button on Page 1)
    • output: RenderCart()
  • page 1: shipping info
  • page 2: payment info
    • input: CaptureBilling()
  • page 3: confirmation
  • page 4: take action, provide receipt

I/O functions are handled by the vcPageContent_ckout class.

Related Pages


  1. For the 2009 rewrite, I initially tried to have the "back" and "next" buttons specify the target form, removing the need for the submitting-form-identifier, but this causes problems under the following circumstances:
    • determining if the user should be allowed to load the requested form when required fields in the current form have been left empty:
      • If the user is moving forward, then NO - the submitting form should be re-displayed with a message listing the missing fields
      • If the user is moving backward, then YES - the requested form should be displayed regardless
    • determining the status of the data on the target page, so as to display the proper status message (indicating what fields, if any, are missing):
      • If this page has never been submitted, then no message should be displayed
      • If this page has been submitted previously, then the stored data should be checked
      • If this page is being re-loaded because the user requested a forward move while leaving one or more required fields blank, then the submitted data must be checked (this rule can be simplified by storing it first and then always checking stored data)