 |
 |
 |
Modeling: User's Guide |  |
 |
|
|
|
|
Modeling: User's Guide | |
|
|
Now suppose that you want to enforce that the value stored in the
lastName attribute does not begin with a 'J'. This sort of
constraint is not expressed within the model, so you have
to write some code for that, and you want that to be checked
transparently, along with other constraints.
The validateValueForKey is ready for such a situation: it expects you to write a method named validateLastName (note the capitalized letter in validateLastName). If it exists, then it gets automatically called. This is how you would write it:
from Modeling import Validation
def validateLastName(self, aValue):
"Checks that the provided value does not begin with a 'J'"
if aValue.find('J')==0:
raise Validation.ValidationException
return
Let's call aWriter.validateValueForKey("Jleese", "lastName") one
more time, catch the exception, and checks its error dictionary:
{ 'lastName': ['Custom validation of key failed'],
}
Our own validation method has been taken into account, as expected, and the value Validation.CUSTOM_KEY_VALIDATION, part of the errors for key lastName, signals it.
|
|
|
Modeling: User's Guide | |
|
|