Sams Teach Yourself C++ in 21 Days

• Account


• Receipts


• ATM (machine)


• Network
  This is not a bad way to start, as far as it goes. You might then go on to diagram the
  obvious relationships among some of these classes, as shown in Figure 11.12.

352 Day 11

FIGURE11.12

Preliminary classes.

Checking Account

Account

AT M

Cash Receipt

Customer

Network

Dispenses Dispenses

Transformations ..............................................................................................

What you began to do in the preceding section was not so much extract the nouns from

the scenario as to begin transforming objects from the domain analysis into objects in the

design. That is a fine first step. Often, many of the objects in the domain have surrogates

in the design. An object is called a surrogate to distinguish between the actual physical

receipt dispensed by an ATM and the object in your design that is merely an intellectual

abstraction implemented in code.

You will likely find that mostof the domain objects have a representation in the design—

that is, a one-to-one correspondence exists between the domain object and the design

object. Other times, however, a single domain object is represented in the design by an

entire series of design objects. And at times, a series of domain objects might be repre-

sented by a single design object.