Code Example: Static vs. Dynamic Binding

Static Binding

The code segment below checks the type of the current Vehicle and calls the corresponding function:

switch (myVehicle->type) {
  case CAR:

              x = stopCar();

    break;

  case PLANE:

              x = stopPlane();

    break;

  case BIKE:

              x = stopBike();

    break;

default:

    error("Invalid");

}

This is difficult and error-prone to maintain, when new types of vehicles are added...

Dynamic Binding

The switch-statement above can be replaced by sending a message to the object which the variable myVehicle currently refers to:

x = myVehicle->stop();

In C++, the variable myVehicle would have been declared to be of type "reference to an instance of class Vehicle, or one of its subclasses":

Vehicle* myVehicle;