public void Visit(Planet planet)
{
// We know we have a SpaceShip and we know this is a Planet
if (planet.Gravity > 3)
{
Console.WriteLine("due to high gravity, the " + this.Name + " crashes into a planet");
}
else
{
Console.WriteLine("the " + this.Name + " lands safely on this wonderful planet");
}
}
public static void Start()
{
Console.WriteLine("\nMultipleDispatchWithVisitor\n");
SpaceShip ship = new SpaceShip() { Name = "enterprise" };
IVisitable a = new Planet() { Gravity = 1 };
IVisitable b = new Planet() { Gravity = 5 };
IVisitable c = new Asteroid() { Metal = 3 };
IVisitable d = new Asteroid() { Metal = 2 };
a.Accept(ship);
b.Accept(ship);
c.Accept(ship);
d.Accept(ship);
// Functionality extracted from visitable to visitor. It would be easy to
// add new visitors.
// Downside:
// - Boilerplate code in visitable
// - Tight coupling between visitor and visitable
// - With every new visitable all visitors need to be amended
}