Definition of a Class Member Function
computer science
Description
Introduction to Classes
The concept of a class is the same as that of a structure: it is a user-defined data type that is used to
create a group of variables that may have different data types.
In addition to the data members, a member of a class can also be a function.
A member function is in general specified in the class definition by its function prototype with its
definition provided somewhere else in the program.
You define a class as follows:
class <class-name>
{
<Data-members-and/or-member functions-declarations>
};
A member of a class (data or function) can be public or private.
In the definition of a class,
you use the label public to specify its public members and
the label private to specify its private members.
Example C1
class Demo1
{
public:
double getValue2(void); // to return the value of the private data member
void setValue2(double num); // to set the value of the private data member
double getAverage( ); // to compute the average of both values
double val1; // the public data member
private:
double computeSum( ); // to compute the sum of both values
double val2; // the private data member
};
©2011 Gilbert Ndjatou Page 208
Definition of a Class Member Function
When you write the definition of a class member function, you must precede the name of the
function in the function header by the name of that class followed by the scope resolution operator
( :: ).
A class data member (public or private) can be accessed in the body of a member function of that
class.
A class member function (private or public) can be called in another member function of that class.
Example C2 Definitions of the member functions of class Demo1:
/*---------------------------------- function getValue2( ) --------------------------------------------------*/
/* returns the value of the private member variable */
double Demo1:: getValue2(void)
{
return (val2);
}
/*---------------------------------- function setValue2( ) --------------------------------------------------*/
/* set the value of the private member variable to the given value */
void Demo1:: setValue2(double num)
{
val2 = num;
}
/*---------------------------------- function getAverage( ) --------------------------------------------------*/
/* compute the average of both values and return it */
double Demo1:: getAverage(void)
{
double total;
total = computeSum( );
return(total / 2);
}
/*---------------------------------- function computeSum( ) ------------------------------------------------*/
/* compute the sum of both values and return it */
double Demo1:: computeSum(void)
{
return (val1 + val2 ) ;
}
©2011 Gilbert Ndjatou Page 209
Declaration of a Class Variable (or Object)
- A class variable is called an object.
- You declare an object in the same way that you declare a structure variable.
- As with structure variables, when you declare an object, a member variable is created for each data
member of the class.
