Validation with Key-Value Coding
As mentioned earlier, there are two opportunities for validation when working with Cocoa controls and bindings. The first, formatters, straddles the view and controller layers of MVC. Once a value is accepted by a formatter, if present, there is a second opportunity for validation via Key-Value Coding (KVC), or, more specifically, by Key-Value Validation. Key-Value Validation is done at the model and/or controller layers. That is, the model objects themselves can opt in to validating changes.
Adding Key-Value validation to RaiseMan
RaiseMan’s users can enter any name for an employee, even the empty string. But they cannot enter just anything for the raise. Although you made the number formatter ...
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