Chapter 13: Object-Oriented Programming: Polymorphism

1. 13.3.1 Invoking Base-Class Functions from Derived-Class Objects
   • CommissionEmployee.h - Same as Fig 12.4
   • CommissionEmployee.cpp - Same as Fig 12.14
   • BasePlusCommissionEmployee.h - Same as Fig 12.10
   • BasePlusCommissionEmployee.cpp - Same as Fig 12.15
   • fig13_01.cpp
     • L.36 Aiming base-class pointer at base-class object.
     • L.42 Aiming derived-class pointer at derived-class object.
     • L.49 Aiming base-class pointer at derived-class object
2. 13.3.2 Aiming Derived-Class Pointers at Base-Class Objects - Error
   • CommissionEmployee.h - Same as Fig 12.4
   • CommissionEmployee.cpp - Same as Fig 12.14
   • BasePlusCommissionEmployee.h - Same as Fig 12.10
   • BasePlusCommissionEmployee.cpp - Same as Fig 12.15
   • fig13_02.cpp
     • Error - L.14 Assigning CommissionEmployee* to BasePlusCommissionEmployee*
3. 13.3.3 Derived-Class Member-Function Calls via Base-Class Pointers - Error
   • CommissionEmployee.h - Same as Fig 12.4
   • CommissionEmployee.cpp - Same as Fig 12.14
   • BasePlusCommissionEmployee.h - Same as Fig 12.10
   • BasePlusCommissionEmployee.cpp - Same as Fig 12.15
   • fig13_03.cpp
     • A BasePlusCommissionEmployee object can be aimed by a CommissionEmployee pointer. However, if you try to access its member fuction getBaseSalary() via the CommisionEmpoloyee pointer, L.26 causes a compilation error.
4. 13.3.4 Virtual Functions
   • CommissionEmployee.h
     1. L.30 Declare earnings() as a virtual function.
     2. L.31 Declare print() as a virtual function.
   • CommissionEmployee.cpp - Same as Fig 12.14
   • BasePlusCommissionEmployee.h
     1. L.20 Declare earnings() as a virtual function.
     2. L.21 Declare print() as a virtual function.
     3. Although this keyword (virtual) can be omitted in derived classes, you should include them for clarity.
   • BasePlusCommissionEmployee.cpp - Same as Fig 12.15
   • fig13_06.cpp
     • L.54 Aim base-class pointer at derived-class object
     • L.61 Polymorphism; invokes BasePlusCommissionEmployee's print()
5. 13.5 Pure virtual Functions and Abstract Classes
   • Employee.h
     • L.24 "virtual double earnings const = 0" declares earnings() as a pure virtual function.
   • Employee.cpp
     • In this file, no implementation is provided for pure virtual function earnings.
     • L.53 provides the implementation of the virtual function print().
   • SalariedEmployee.h
     • L.18 Declare a virtual function earnings().
     • L.19 Declare a virtual function print().
   • SalariedEmployee.cpp
     • L.41 Don't forget this scope resolution operator. Otherwise you will get recursive function calls.
   • CommissionEmployee.h
     • L.8 Class CommissionEmployee derives from Employee.
     • L.21 Declare earnings() as a virtual function.
     • L.22 Declare print() as a virtual function.
   • CommissionEmployee.cpp
     • L.10 The constructor passes the first name, last name and social security number to the Employee constructor.
     • L.56 Fucntion print() calls base-class function print() to display the Employee-specific information.
   • BasePlusCommissionEmployee.h - Same as Fig. 13.5
   • BasePlusCommissionEmployee.cpp - Same as Fig. 12.15
   • fig13_17.cpp
     • L.62 A reference to the object is obtained by dereferencing the pointer.
     • L.77 Each call to virtualViaReference invokes virtual function earnings via reference baseClassRef to demonstrate polymorphism.
6. 13.8 Rumtime Type Information
   • Employee.h - Same as Fig. 13.9
   • Employee.cpp - Same as Fig. 13.10
   • SalariedEmployee.h - Same as Fig. 13.11
   • SalariedEmployee.cpp - Same as Fig. 13.12
   • CommissionEmployee.h - Same as Fig. 13.13
   • CommissionEmployee.cpp - Same as Fig. 13.14
   • BasePlusCommissionEmployee.h - Same as Fig. 13.5
   • BasePlusCommissionEmployee.cpp - Same as Fig. 12.15
   • fig13_19.cpp
     • L.8 #include
     • L.39 dynamic_cast() - downcast
     • L.46 This cannot be a base-class pointer, because getBaseSalary() is a derived-class-only member function.
     • L.61 typeid().name()