Factory Pattern without a Switch or If/Then

Question

I\'m looking for a simple example of how to implement a factory class, but without the use of a Switch or an If-Then statement. All the examples I can find use one. F

Answer 1

How about this (no Dictionary required and note that you will get an syntax error if your try to Create()):

EDIT - Updated to use an IPosition interface implemented explicitly. Only instances of IPosition can access the member functions (e.g. .Title will not compile).

EDIT #2 Factory.Create should return an IPosition not T when using the interface properly.

using System;
using System.Collections.Generic;

class Program
{
    interface IPosition
    {
        string Title { get; }
        bool RequestVacation();
    }

    class Manager : IPosition
    {
         string IPosition.Title
        {
            get { return "Manager"; }
        }

        bool IPosition.RequestVacation()
        {
            return true;
        }
    }

    class Clerk : IPosition
    {
        int m_VacationDaysRemaining = 1;

        string IPosition.Title
        {
            get { return "Clerk"; }
        }

        bool IPosition.RequestVacation()
        {
            if (m_VacationDaysRemaining <= 0)
            {
                return false;
            }
            else
            {
                m_VacationDaysRemaining--;
                return true;
            }
        }
    }

    class Programmer : IPosition
    {
        string IPosition.Title
        {
            get { return "Programmer"; }
        }

        bool IPosition.RequestVacation()
        {
            return false;
        }
    }

    static class Factory
    {
        public static IPosition Create() where T : IPosition, new ()
        {
            return new T();
        }
    }

    static void Main(string[] args)
    {
        List positions = new List(3);
        positions.Add(Factory.Create());
        positions.Add(Factory.Create());
        positions.Add(Factory.Create());

        foreach (IPosition p in positions) { Console.WriteLine(p.Title);  }
        Console.WriteLine();

        Random rnd = new Random(0);
        for (int i = 0; i < 10; i++)
        {
            int index = rnd.Next(3);
            Console.WriteLine("Title: {0}, Request Granted: {1}", positions[index].Title, positions[index].RequestVacation());
        }

        Console.ReadLine();
    }
}