Question

I’m dealing with a Parallel Inheritance Hierarchy and I have an idea for a step by step refactoring and would like opinions on whether it will work or whether there is a better way to do it.

1. Create a Handler class with children that implement the specific behavior required e.g CarHandler with children vwHandler, fordHandler, bmwHandler

2. Add calls to all the components and restructure it so that the children return the objects neccessary. e.g. Call vwHandler.getDrive will return the result of vwDrive.drive, call vwHandler.getSeat returns vwSeat.seat)

3. Refactor the other classes so that they provide general functionality rather than specific e.g. Call vwHandler.getDrive will return drive(vwSpec1, vwSpec2)

Example of Handler

public abstract class CarHandler
{
   private Car car;

   public Car getCar()
   {
       return car;
   }
   public Car setCar()
   {
       car = car;
   }

   public CarHandler(Car car)
   {
       this.car = car;
   }

   public Car getCar()
   {
       return car;
   }

   public void setCar(Car car)
   {
       this.car = car;
   }

   public void updateCar()
   {
       Globalizer.updateOnServer(car);
   }

   public abstract Drive getNewDrive();
   public abstract Seat getNewSeat();    
}

Answer 1

This approach is working quite well for me actually, I’ve implemented the first two steps and ended up removing several hundred lines of duplication as well as getting a good look at how to further refactor in future. I would highly recommend this approach.