Chapter 10: Classes: A Deeper Look, Part2

• 10.2 const (Constant) Objects and const Member Functions
  • Time.h
    • To specify a member function as const, insert the keyword const after the function's parameter list.
  • Time.cpp
    • The fact that a member function does not modify an object is not sufficient. You must explicitly declare it as const.
  • fig10_03.cpp
    • If the program attempts to invoke non-const member fuctions on a const object, the compiler generates an error message.
• Member Initializer List (P.452)
  • Increment.h
    • This class contains non-const data member "count" and const data member "increment".
  • Increment.cpp
    • The constructor initializes data members with a member initializer list
  • Invoking an Increment object's print and addIncrement member functions.
• Erroneously Attempting to Initialize a const Data Member with an Assignment (P.454)
  • Increment.h
    • Same as the above
  • Increment.cpp
    • Attempt to initialize const data member "increment" with an assignment statement
  • consterror.cpp
    • Same as the above
• 10.3 Composition: Objects as Members of Classes
  • Date class definition
  • Date class member-function implementation
  • Employee.h
    • An Employee object is composed of two string objects plus two Date objects.
  • Empoyee.cpp
    • constructor uses member initializer list to pass initializer values of member objects.
  • Demonstrating composition - an object with member objects.
    • The program displays 3 constructor calls and 5 destructor calls. The missing two are the default destructor calls.
    • Objects are constructed from the inside out and destroyed in the reverse order, from the outside in.
• 10.4 friend Functions and friend Classes
  • Friends can access private members of a class.
  • Although friend declaration can appear anywhere in the class, conventionally it will appear first, even before the public specifier.
• 10.5 Using the this Pointer
  • Note the parentheses around *this when used with the dot member selection operator (.). The parentheses are required because the dot operator has higher precedence than the * operator.
• Cascaded Function Calls
  • Time.h
    • Time class modified to enable cascaded member-function calls
    • Note that setTime() returns Time&
    • Compared with Fig. 10.1, where setTime() returns void.
  • Time.cpp
    • setTime() returns *this to enable cascading.
  • Cascading member-function calls with the "this" pointer
    • Line 12: t.setHour(18).setMinute(30).setSecond(22);
• 10.6 static Class Members
  • Employee.h
    • Use a static data member to track the number of Employee objects in memory
  • Employee.cpp
    • Initialize at global namespace scope, without including the keyword "static". (At global namespace scope, "static" means that item will be known only in that file.) (Honestly, it should be "private", but at the time C language was created, they decided to "overload" these keywords heavily. "void*" is another example, which should be "any*".)
    • In the constructor, ++count
    • In the destructor, --count
  • Track the number of objects of a class (with static data member)
• 10.7 Proxy Classes
  • Implementation.h
  • Interface.h
    • You don't need to "#include Implementation.h".
    • But "forward class declaration" is required by Line 6 "class Implementation;".
  • Interface.cpp
    • This is the only file which knows the implementation details (#include "Implementation.h").
  • fig11_19.cpp
    • Hiding private data of Implementation with a proxy class Interface.