Monday, May 6, 2013

Published 2:39 AM by with 0 comment

Composite Design Pattern - [Structural Patterns]



Composite Pattern

[Download cs c#] 

Definition

Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly.



    //Component class
    abstract class Component
    {
        protected string name;

        public Component(string name)
        {
            this.name = name;
        }

        public abstract void Add(Component c);
        public abstract void Remove(Component c);
        public abstract void Display(int Dept);
    }

    //Composite Class
    class Composite : Component
    {
        private List<Component> _com = new List<Component>();

        public Composite(string name):base(name)
        {

        }
        public override void Add(Component c)
        {
            _com.Add(c);
        }
        public override void Remove(Component c)
        {
            _com.Remove(c);
        }
        public override void Display(int Dept)
        {
            Console.WriteLine(new String('-',Dept)+name);

            foreach (Component component in _com)
            {
                component.Display(Dept + 2);
            }
        }
    }

        //Leaf Class
        class Leaf : Component
        {
            public Leaf(string name):base(name)
            {

            }
            public override void Add(Component c)
            {
                Console.WriteLine("Can not add to a leaf");
            }
            public override void Remove(Component c)
            {
                Console.WriteLine("Can not remove from a leaf");
            }
            public override void Display(int Dept)
            {
                Console.WriteLine(new String('-', Dept) + name);
            }
        }



            //---Composite Calling...
            Composite root = new Composite("root");
            root.Add(new Leaf("Leaf A"));
            root.Add(new Leaf("Leaf B"));

            Composite comp = new Composite("Composite X");
            comp.Add(new Leaf("Leaf XA"));
            comp.Add(new Leaf("Leaf XAB"));

            root.Add(comp);
            root.Add(new Leaf("Leaf C"));

            // Add and remove a leaf
            Leaf leaf = new Leaf("Leaf D");
            root.Add(leaf);
            root.Remove(leaf);

            // Recursively display tree
            root.Display(1);

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Sunday, May 5, 2013

Published 11:24 PM by with 0 comment

Observer Pattern - [Behavioral Patterns]


Observer Pattern 

[Download cs c#]

Definition

Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.



    //Observer Class
    abstract class Observer
    {
        public abstract void Update();
    }


    //Subject Class
    abstract class Subject
    {
        private List<Observer> _observer = new List<Observer>();

        public void Register(Observer obs)
        {
            _observer.Add(obs);
        }

        public void Unregister(Observer obs)
        {
            _observer.Remove(obs);
        }

        public void Notify()
        {
            foreach (Observer obs in _observer)
            {
                obs.Update();
            }
        }
    }

    //StockMarket Class
    class StockMarket : Subject
    {
        private string _subjectState;

        public string SubjectState
 {
get
{
 return _subjectState;
}
set
{
 _subjectState = value;
}
}
    }


    //GoogleStockGadet Class
    class GoogleStockGadet  : Observer
    {
        private string _name;
        private string _observerState;
        private StockMarket _concreteSubject;

        public GoogleStockGadet(StockMarket conSubject, string name)
        {
            _concreteSubject = conSubject;
            _name = name;
        }

        public override void Update()
        {
            _observerState = _concreteSubject.SubjectState;
            Console.WriteLine("Observer {0}'s new state is {1}", _name, _observerState);
        }

        public StockMarket Subject
 {
 get
 {
return _concreteSubject;
 }
 set
 {
 _concreteSubject = value;
 }
 }
    }

    //MSNStockGadget Class
    class MSNStockGadget  : Observer
    {
        private string _name;
        private string _observerState;
        private StockMarket _concreteSubject;

        public MSNStockGadget(StockMarket conSubject, string name)
        {
            _concreteSubject = conSubject;
            _name = name;
        }

        public override void Update()
        {
            _observerState = _concreteSubject.SubjectState;
            Console.WriteLine("Observer {0}'s new state is {1}", _name, _observerState);
        }

        public StockMarket Subject
 {
get
{
return _concreteSubject;
}
Set
{
_concreteSubject = value;
}
 }
    }


    //YahooStockGadget Class
    class YahooStockGadget  : Observer
    {
        private string _name;
        private string _observerState;
        private StockMarket _concreteSubject;

        public YahooStockGadget(StockMarket conSubject, string name)
        {
            _concreteSubject = conSubject;
            _name = name;
        }

        public override void Update()
        {
            _observerState = _concreteSubject.SubjectState;
            Console.WriteLine("Observer {0}'s new state is {1}", _name, _observerState);
        }

        public StockMarket Subject
 {
 get
 {
 return _concreteSubject;
 }
 Set
 {
_concreteSubject = value;
 }
 }
    }

            //Calling...
            StockMarket s = new StockMarket();

            s.Register(new GoogleStockGadet(s, "X"));
            s.Register(new MSNStockGadget(s, "Y"));
            s.Register(new YahooStockGadget(s, "Y"));

            s.SubjectState = "ABC";
            s.Notify();


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