Case Study: Payroll System Using Polymorphism

• Base class Employee
  • Pure virtual function earnings (returns pay)
    • Pure virtual because need to know employee type
    • Cannot calculate for generic employee
  • Other classes derive from Employee

  Figure 5.26: Class hierarchy for the polymorphic employee-payroll application.

  
• Downcasting
  • dynamic_cast operator
    • Determine object's type at runtime
    • Returns 0 if not of proper type (cannot be cast)
    • NewClass *ptr = dynamic_cast < NewClass *> objectPtr;
• Keyword typeid
  • Header <typeinfo>
  • Usage: typeid(object)
    • Returns type_info object
    • Has information about type of operand, including name
    • typeid(object).name()

Figure 5.27: Employee class header file.

Figure 5.28: Employee class implementation file. (part 1 of 2)

Figure 5.29: Employee class implementation file (part 2 of 2) and SalariedEmployee class header file.

Figure 5.30: SalariedEmployee class implementation file.

Figure 5.31: HourlyEmployee class header file.

Figure 5.32: HourlyEmployee class implementation file.

Figure 5.33: CommissionEmployee class header file.

Figure 5.34: CommissionEmployee class implementation file.

Figure 5.35: BasePlusCommissionEmployee class header file.

Figure 5.36: BasePlusCommissionEmployee class implementation file.

Figure 5.37: Employee class hierarchy driver program.(part 1 of 2)

Figure 5.38: Employee class hierarchy driver program.(part 2 of 2)