Delegation is a design pattern that combines object composition and inheritance. Basically, it is a mechanism where one object delegates actions to another. To see it in action, let's take a look how we would achieve delegation in Java:
public interface Drivable {
void drive();
}
public class Car implements Drivable {
@Override
public void drive() {
System.out.println("Driving a car");
}
}
public class Vehicle implements Drivable {
private Car car;
public Vehicle(Car car) {
this.car = car;
}
@Override
public void drive() {
car.drive();
}
}
public void driveVehicle() {
Car car = new Car();
Vehicle vehicle = new Vehicle(car);
vehicle.drive(); // with delegation, car.drive() get's called
}In this example, we have the Drivable interface and two classes that implement it. The Vehicle class doesn't have its own drive functionality; rather, it delegates the drive function to the Car object.
If we were to write the same example in Kotlin, it would look like this:
interface Drivable...