11.3.1. Creating and Using a CommissionEmployee Class
Let’s examine CommissionEmployee’s class definition (Figs. 11.4–11.5). The CommissionEmployee header (Fig. 11.4) specifies class CommissionEmployee’s public services, which include a constructor (lines 11–12) and member functions earnings (line 29) and print (line 30). Lines 14–27 declare public get and set functions that manipulate the class’s data members (declared in lines 32–36) firstName, lastName, socialSecurityNumber, grossSales and commissionRate. Member functions setGrossSales (defined in lines 57–63 of Fig. 11.5) and setCommissionRate (defined in lines 72–78 of Fig. 11.5), for example, validate their arguments before assigning the values to data members grossSales and commissionRate, respectively.
1 // Fig. 11.4: CommissionEmployee.h
2 // CommissionEmployee class definition represents a commission employee.
3 #ifndef COMMISSION_H
4 #define COMMISSION_H
5
6 #include <string> // C++ standard string class
7
8 class CommissionEmployee
9 {
10 public:
11 CommissionEmployee( const std::string &, const std::string &,
12 const std::string &, double = 0.0, double = 0.0 );
13
14 void setFirstName( const std::string & ); // set first name
15 std::string getFirstName() const; // return first name
16
17 void setLastName( const std::string & ); // set last name
18 std::string getLastName() const; // return last name
19
20 void setSocialSecurityNumber( const std::string & ); // set SSN
21 std::string getSocialSecurityNumber() const; // return SSN
22
23 void setGrossSales( double ); // set gross sales amount
24 double getGrossSales() const; // return gross sales amount
25
26 void setCommissionRate( double ); // set commission rate (percentage)
27 double getCommissionRate() const; // return commission rate
28
29 double earnings() const; // calculate earnings
30 void print() const; // print CommissionEmployee object
31 private:
32 std::string firstName;
33 std::string lastName;
34 std::string socialSecurityNumber;
35 double grossSales; // gross weekly sales
36 double commissionRate; // commission percentage
37 }; // end class CommissionEmployee
38
39 #endif
Fig. 11.4. CommissionEmployee class header.
1 // Fig. 11.5: CommissionEmployee.cpp
2 // Class CommissionEmployee member-function definitions.
3 #include <iostream>
4 #include <stdexcept>
5 #include "CommissionEmployee.h" // CommissionEmployee class definition
6 using namespace std;
7
8 // constructor
9 CommissionEmployee::CommissionEmployee(
10 const string &first, const string &last, const string &ssn,
11 double sales, double rate )
12 {
13 firstName = first; // should validate
14 lastName = last; // should validate
15 socialSecurityNumber = ssn; // should validate
16 setGrossSales( sales ); // validate and store gross sales
17 setCommissionRate( rate ); // validate and store commission rate
18 } // end CommissionEmployee constructor
19
20 // set first name
21 void CommissionEmployee::setFirstName( const string &first )
22 {
23 firstName = first; // should validate
24 } // end function setFirstName
25
26 // return first name
27 string CommissionEmployee::getFirstName() const
28 {
29 return firstName;
30 } // end function getFirstName
31
32 // set last name
33 void CommissionEmployee::setLastName( const string &last )
34 {
35 lastName = last; // should validate
36 } // end function setLastName
37
38 // return last name
39 string CommissionEmployee::getLastName() const
40 {
41 return lastName;
42 } // end function getLastName
43
44 // set social security number
45 void CommissionEmployee::setSocialSecurityNumber( const string &ssn )
46 {
47 socialSecurityNumber = ssn; // should validate
48 } // end function setSocialSecurityNumber
49
50 // return social security number
51 string CommissionEmployee::getSocialSecurityNumber() const
52 {
53 return socialSecurityNumber;
54 } // end function getSocialSecurityNumber
55
56 // set gross sales amount
57 void CommissionEmployee::setGrossSales( double sales )
58 {
59 if ( sales >= 0.0 )
60 grossSales = sales;
61 else
62 throw invalid_argument( "Gross sales must be >= 0.0" );
63 } // end function setGrossSales
64
65 // return gross sales amount
66 double CommissionEmployee::getGrossSales() const
67 {
68 return grossSales;
69 } // end function getGrossSales
70
71 // set commission rate
72 void CommissionEmployee::setCommissionRate( double rate )
73 {
74 if ( rate > 0.0 && rate < 1.0 )
75 commissionRate = rate;
76 else
77 throw invalid_argument( "Commission rate must be > 0.0 and < 1.0" );
78 } // end function setCommissionRate
79
80 // return commission rate
81 double CommissionEmployee::getCommissionRate() const
82 {
83 return commissionRate;
84 } // end function getCommissionRate
85
86 // calculate earnings
87 double CommissionEmployee::earnings() const
88 {
89 return commissionRate * grossSales;
90 } // end function earnings
91
92 // print CommissionEmployee object
93 void CommissionEmployee::print() const
94 {
95 cout << "commission employee: " << firstName << ' ' << lastName
96 << "
social security number: " << socialSecurityNumber
97 << "
gross sales: " << grossSales
98 << "
commission rate: " << commissionRate;
99 } // end function print
Fig. 11.5. Implementation file for CommissionEmployee class that represents an employee who is paid a percentage of gross sales.
CommissionEmployee Constructor
The CommissionEmployee constructor definition purposely does not use member-initializer syntax in the first several examples of this section, so that we can demonstrate how private and protected specifiers affect member access in derived classes. As shown in Fig. 11.5, lines 13–15, we assign values to data members firstName, lastName and socialSecurityNumber in the constructor body. Later in this section, we’ll return to using member-initializer lists in the constructors.
We do not validate the values of the constructor’s arguments first, last and ssn before assigning them to the corresponding data members. We certainly could validate the first and last names—perhaps by ensuring that they’re of a reasonable length. Similarly, a social security number could be validated to ensure that it contains nine digits, with or without dashes (e.g., 123-45-6789 or 123456789).
CommissionEmployee Member Functions earnings and print
Member function earnings (lines 87–90) calculates a CommissionEmployee’s earnings. Line 89 multiplies the commissionRate by the grossSales and returns the result. Member function print (lines 93–99) displays the values of a CommissionEmployee object’s data members.
Testing Class CommissionEmployee
Figure 11.6 tests class CommissionEmployee. Lines 11–12 instantiate CommissionEmployee object employee and invoke the constructor to initialize the object with "Sue" as the first name, "Jones" as the last name, "222-22-2222" as the social security number, 10000 as the gross sales amount and .06 as the commission rate. Lines 19–24 use employee’s get functions to display the values of its data members. Lines 26–27 invoke the object’s member functions setGrossSales and setCommissionRate to change the values of data members grossSales and commissionRate, respectively. Line 31 then calls employee’s print member function to output the updated CommissionEmployee information. Finally, line 34 displays the CommissionEmployee’s earnings, calculated by the object’s earnings member function using the updated values of data members grossSales and commissionRate.
1 // Fig. 11.6: fig11_06.cpp
2 // CommissionEmployee class test program.
3 #include <iostream>
4 #include <iomanip>
5 #include "CommissionEmployee.h" // CommissionEmployee class definition
6 using namespace std;
7
8 int main()
9 {
10 // instantiate a CommissionEmployee object
11 CommissionEmployee employee(
12 "Sue", "Jones", "222-22-2222", 10000, .06 );
13
14 // set floating-point output formatting
15 cout << fixed << setprecision( 2 );
16
17 // get commission employee data
18 cout << "Employee information obtained by get functions:
"
19 << "
First name is " << employee.getFirstName()
20 << "
Last name is " << employee.getLastName()
21 << "
Social security number is "
22 << employee.getSocialSecurityNumber()
23 << "
Gross sales is " << employee.getGrossSales()
24 << "
Commission rate is " << employee.getCommissionRate() << endl;
25
26 employee.setGrossSales( 8000 ); // set gross sales
27 employee.setCommissionRate( .1 ); // set commission rate
28
29 cout << "
Updated employee information output by print function:
"
30 << endl;
31 employee.print(); // display the new employee information
32
33 // display the employee's earnings
34 cout << "
Employee's earnings: $" << employee.earnings() << endl;
35 } // end main
Employee information obtained by get functions:
First name is Sue
Last name is Jones
Social security number is 222-22-2222
Gross sales is 10000.00
Commission rate is 0.06
Updated employee information output by print function:
commission employee: Sue Jones
social security number: 222-22-2222
gross sales: 8000.00
commission rate: 0.10
Employee's earnings: $800.00
Fig. 11.6. CommissionEmployee class test program.