Sams Teach Yourself C in 21 Days

Working with C++ Classes and Objects 695

BD3

Person brad: Bradley Jones

age: 21

Person blank: blank blank

age: -1

Employee kyle: Kyle Rinne

age: 32

salary: 50000

Much of this listing is the same as the previous listing. You can see that the per-

sonclass has been declared just as it was in Listing B3.7. The new code has been

bolded to make it easier for you to see where the changes are.

In line 21 you see the first real changes. One of these is the declaration for the employee

class. This declaration is presented as

class employee : public person {

Just as in a regular class, the employee definition starts off with the keyword class fol-

lowed by the name of the new class—employee, in this case. What is new is the colon

and the text which follows. The colon indicates that employeeis a subclass. The name of

the base class to which employeeis a subclass is then presented—person, in this case.

Thepublickeyword provides access to the components of the personclass to the

employeeclass. If you were creating a subclass called student, you would start the defi-

nition off with

class student : public person {

Additionally, if you were going to use employeeas a base class to create a new class

calledtemp_employee, you would start the definition off with

class temp_employee : public employee {

Thetemp_employeeinherits from employee. You should note that because employee

inherits from person,temp_employeealso has access to the personmembers and fea-

tures. Figure B3.1 illustrates these inheritance structures.

Looking back at Listing B3.8, you can see that the declaration for the employeeclass is

relatively short. The employeeclass is short in this case because it also contains every-

thing in the personclass. Only those things that are new or different are added to this

class. In this case, that means a single data member called salary, two access functions

forsalary, and a constructor.

Implementing the Subclass Constructor

In lines 46–50 you see the employeeclass’s constructor. Again, you should notice that

this constructor is different from the personclass’s constructor. The first part of the con-

structor’s header is the same:

OUTPUT

ANALYSIS

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