Factory design pattern

Define an interface for creating an object, but let the subclasses decide which class to instantiate. The Factory method lets a class defer instantiation to subclasses." Factory methods encapsulate the creation of objects. This can be useful if the creation process is very complex, for example if it depends on settings in configuration files or on user input.

Goal:

Only creating objects

A C# example of the Factory Pattern

// A Simple Interface

public interface IVehicle

{

    void Drive(int miles);

}

// The Vehicle Factory

public class VehicleFactory

{

    public static IVehicle getVehicle(string Vehicle)

    {

        switch (Vehicle) {

            case "Car":

                return new Car();

            case "Lorry":

                return new Lorry();

            default:

                throw new ApplicationException(string.Format("Vehicle '{0}' cannot be created", Vehicle));

                break;

        }

    }

}

// A Car Class that Implements the IVehicle Interface

public class Car : IVehicle

{

    public void IVehicle.Drive(int miles)

    {

        // Drive the Car

    }

}

// A Lorry Class that Implements the IVehicle Interface

public class Lorry : IVehicle

{

    public void IVehicle.Drive(int miles)

    {

        // Drive the Lorry

    }

}

Example code Download here :FactoryExa