Sams Teach Yourself C++ in 21 Days

Containment Often, one object is composed of many subobjects. For example, a car

is composed of a steering wheel, tires, doors, radio, and so forth. A checking account is

composed of a balance, a transaction history, a customer ID, and so on. The checking

account hasthese items; containment models the “has a”relationship. The UML illus-

trates the containment relationship by drawing a line with a diamond from the containing

object to the contained object, as shown in Figure 11.6.

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FIGURE11.6

Containment. Checking Account

Balance

Aggregation

The diagram in Figure 11.6 suggests that the Checking Account has aBalance. You can

combine these diagrams to show a fairly complex set of relationships (see Figure 11.7).

FIGURE11.7

Object relationships.

Bank Account

Checking Account Savings Account

Balance Transaction History