8.5. User defined check routines

User-defined check routines can be defined with CodeDef in a file included in the code/ directory, the same as a UserTag.

 CodeDef foo  OrderCheck
 CodeDef foo Routine <<EOR
 sub {
        # $ref is to Vend::Session->{'values'} hash
        # $var is the passed name of the variable
        # $val is current value of checked variable
        my($ref, $var, $val) = @_;

     my($ref, $var, $val) = @_;

        if($val ne 'bar') {
                return (undef, $var, "The value of foo must be bar");
     }
     else {
         return (1, $var, '');
     }
 }
 EOF

Now you can specify in an order profile:

  foo_variable=foo

Very elaborate checks are possible. The return value of the subroutine should be a three-element array, consisting of:

1. the pass/fail ('1' or 'undef') status of the check;
2. the name of the variable which was checked;
3. a standard error message for the failure, in case a custom one has not been specified in the order profile.

The latter two elements are used by the [error] tag for on-screen display of form errors. The checkout page of the Foundation demo includes examples of this.