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Totally Immersed: C++ Classes and Object-Oriented Programming
Each instance of your class gets its own copy of the class’s data members in memory. The
exception to this is that if any class data members are declared with the static storage
modifier, all instances of the class will share the same copy of that data member in memory.
In that case only one copy of that data member will exist in memory. If any one instance of the
class changes a static data member, it changes in all the classes. Use of static data members
in classes is not common, so don’t worry about it if this doesn’t make sense right now.
HOUSE RULES: CLASS DATA MEMBERS
■ Use as many data members as you need for vital class operations, but use local
variables where possible.
■ Don’t make all data members public.
■ Use getters and setters for data members that you want to remain private but that
you need to be able to access.
■ Validate data in your setters to ensure that improper values are not being input.
■ Initialize all data members either in the initializer list or in the body of your
constructor.
■ Don’t forget to delete any data members that dynamically allocate memory.
Member Functions
Class member functions are functions that belong to your class. They are local to the class and
do not exist outside the class. Class member functions can be called only from within the class
itself or through an instance of the class. They have access to all public, protected, and private
data members of the class. Member functions can be declared in the private, protected, or
public sections of your class. Good class design requires that you think about which of these
sections your member functions should go into.
Public member functions represent the user interface to the class. It is through the public
member functions that users of the class access the class in order to gain whatever
functionality the class provides. For example, let’s say you have a class that plays and records
wave audio. Public member functions might include functions like Open(), Play(), Record(),
Save(), Rewind(), and so on.
Private member functions are functions that the class uses internally to do its thing. These
functions are not intended to be called by users of the class; they are private in order to be
hidden from the outside world. Frequently a class has startup chores to perform when the class
is created. (For example, you have already seen that the constructor is called when a class is
created.) In some classes the startup processing might be significant, requiring many lines of
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