There are two aspects to data validation:
• Specifying the validation rules
• Implementing them
In this hour, you learn how to set some validation rules for a data model and how they take effect as people enter data. After that, you learn how to modify the default behavior so that you provide your own validation error messages.
The focus in this hour is on the rules. Once you have them in place, some will be managed automatically for you—particularly on Mac OS with its bindings ...