Double Dispatch with an Inverted Visitor Pattern
By David Gould, May 01, 1998
It's hard to model a two-dimensional table with an inheritance tree, but you can come close.
May 1998/Double Dispatch with an Inverted Visitor Pattern/Listing 1
class Event // our "Visitor"
{
public:
virtual visitWidget(Widget&)
{ /* default visitation */ }
virtual visitDerivedWidget(DerivedWidget&)
{ /* default visitation */ }
};
class DerivedEvent
{
public:
virtual visitWidget(Widget&) { /* overridden */ }
virtual visitDerivedWidget(DerivedWidget&) { /* overridden */ }
};
class Widget // our "Element"
{
public:
virtual accept(Event& e) { e.visitWidget(*this); }
};
class DerivedWidget : public Widget
{
public:
virtual accept(Event& e) { e.visitDerived(*this); }
};
/* End of File */
