by John
Kopp
Introduction Welcome to About.com's
free tutorial on C++ programming. This lesson covers static
class members and methods. Static members provide a way to
create objects that are shared by an entire class, rather than
being part of a particular instance of the class, an object.
Static methods provide a way to access and update static
members.
Static Members Suppose it's necessary
to keep track of some data that's related to a class
as a whole, rather than to a particular object
or instance of that class. A simple example is a count of the
total number of objects instantiated.
Maybe we have an Employee class and we want to keep track of
the total number of employees. We could create a global
variable to hold this data.
class
Employee { .... }
int
numEmployees;
main() { Employee
janitor; numEmployees++;
Employee
manager; numEmployees++;
..... }
| While this approach will work,
it has a major short fall. The global variable, numEmployees
is not really related to the class Employee. Ideally, we want
all data associated with the class to be encapsulated
within that class. Although in this simple example it is
obvious that numEmployees pertains to the Employee class, in
larger programs the relationship might not apparent. The
static keyword provides a way to declare that an object is to
be shared by all instances of a class. Here's an
example.
Next
page > Example
of Static Members > Page 1,
2,
3,
4
|