Page 218 - DCAP404 _Object Oriented Programming
P. 218
Unit 10: Virtual Functions and Polymorphism
virtual return_type function_name3( arguments); Notes
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};
To make a member function virtual, the keyword virtual is used in the methods while it is
declared in the class definition but not in the member function definition. The keyword virtual
precedes the return type of the function name. The compiler gets information from the keyword
virtual that it is a virtual function and not a conventional function declaration.
Example: The following declaration of the virtual function is valid.
class point {
intx;
inty;
public:
virtual int length ( );
virtual void display ( );
};
Remember that the keyword virtual should not be repeated in the definition if the definition
occurs outside the class declaration. The use of a function specifier virtual in the function definition
is invalid.
Example:
class point {
intx;
inty;
public:
virtual void display ();
};
virtual void point: : display () //error
{
Function Body
}
A virtual function cannot be a static member since a virtual member is always a member of a
particular object in a class rather than a member of the class as a whole.
class point {
int x;
int y;
public:
virtual static int length (); //error
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