 |
|
|
|
|
|
|
|
|
|
|
|
| • |
Pure
polymorphism requires four things to happen before it
|
|
is in
effect.
|
|
|
| • |
First,
we must have an inheritance hierarchy using public
|
|
|
derivation.
|
|
|
| • |
Second,
we must declare a public member function to be
|
|
|
virtual
in either a direct or indirect base class.
|
|
|
| • |
Third,
an overridden member function implemented in a
|
|
|
derived
class must have exactly the same signature and
|
|
|
return
type as the virtual function declaration.
|
|
|
| • |
Fourth,
the overridden function must be accessed through a
|
|
|
direct
or indirect base class pointer or reference.
|
|
