Value Object Participants

The Client class uses Value instances like built-in datatypes (to the extent that this is possible with your implementation language). Whenever the Client wants to change the value of one of its attributes, it replaces the attribute object rather than changing it. You write code like

attr = attr.calculate();

attr.calculate();

The Value class represents a domain-specific value type. It is implemented such that Value instances are immutable objects, meaning that its instances cannot change their state. Rather, as the result of some computation, a new Value instance with the desired internal state is returned.