Abstract Factory Pattern With Generic Usage

Hi ,

   I want to use abstract factory pattern with generics. So i wrote a generic gauge factory which is below. I have "HalfGauge" and "QuarterGauge" abstract classes. I have concrete classes 'TotalHalfGauge','NewHalfGauge','FrequencyHalfGauges' ,'TotalQuarterGauge','NewQuarterGauge','FrequencyQuarterGauges which inherites HalfGauge or QuarterGauges.

       public class GenericGaugeFactory<T, K> : IGenericGaugeFactory<T, K>
        where T : HalfGauge, new()
        where K : QuarterGauge, new()
   {

                private static GenericGaugeFactory<T, K> _instance;
                private static object lockObject = new object();
                public static GenericGaugeFactory<T, K> Instance
                {
                    get
           {
                if (_instance == null)
                {
                    lock (lockObject)
                    {
                        if (_instance == null)
                            _instance = new GenericGaugeFactory<T, K>();
                    }
                }
                return _instance;
            }
            set { _instance = value; }
        }

        public GenericGaugeFactory() { }

        public T CreateHalfGauge()
        {
            return new T();
        }
        public K CreateQuarterGauge()
        {
            return new K();
        }
    }


Now in my client i want to access my GenericGaugeFactory class like below which takes a GaugeKpiTypes.In switch case blocks i always declare new variables.I dont want this.

I only declare a common variable like below but it gives error. How can i achive this

     IGenericGaugeFactory<HalfGauge, QuarterGauge> _gaugeFactory2 = null;

        switch (GaugeKpis)
        {
            case GaugeKpiEnums.Total: { _gaugeFactory2 = new GenericGaugeFactory<TotalHalfGauge, TotalQuarterGauge>(); break; }
            case GaugeKpiEnums.New: { _gaugeFactory2 = new GenericGaugeFactory<NewHalfGauge, NewQuarterGauge>(); break; }
            case GaugeKpiEnums.Frequency: { _gaugeFactory2 = new GenericGaugeFactory<FrequencyHalfGauge, FrequencyQuarterGauge>(); break; }
            case GaugeKpiEnums.Unique: { _gaugeFactory2 = new GenericGaugeFactory<UniqueHalfGauge, UniqueQuarterGauge>(); break; }
            case GaugeKpiEnums.UniqueTotal: { _gaugeFactory2 = new GenericGaugeFactory<UniqueTotalHalfGauge, UniqueTotalQuarterGauge>(); break; }
            case GaugeKpiEnums.Dwell: { _gaugeFactory2 = new GenericGaugeFactory<DwellTimeHalfGauge, DwellTimeQuarterGauge>(); break; }
            case GaugeKpiEnums.Retention: { _gaugeFactory2 = new GenericGaugeFactory<RetentiontimeHalfGauge, RetentiontimeQuarterGauge>(); break; }
        }

Thanks For your helps.

Best Regards.

Volkan Genç, Dec 03, 2012

Reply 1

Hi,

I Can do it with Covarience like below sample. I want to handle common variable.

     public class Program
    {
        static void Main(string[] args)
        {



            IGenericFactory<IAnimal> hayvan = new GenericFactory<Cat>();
            hayvan = new GenericFactory<Dog>();

            IAnimal cat = hayvan2.Create();
            cat.Speak();
            Console.ReadLine();

        }
    }

   public interface IAnimal
    {
        void Speak();
    }

    public class Cat : IAnimal
    {
        public void Speak()
        {
            Console.WriteLine("Miyaww");
        }
    }

    public class Dog : IAnimal
    {
        public void Speak()
        {
            Console.WriteLine("Hqw haww");
        }
    }

    public interface IGenericFactory<out T>
    {
        T Create();
    }

    public class GenericFactory<T> : IGenericFactory<T> where T : IAnimal, new()
    {

        public GenericFactory() { }

        public T Create()
        {
            return new T();
        }

    }

Best Regards.

Volkan Genç, Apr 18, 2013