C#面向对象设计模式纵横谈——19 Observer观察者模式

主讲：李建忠

来源：http://www.microsoft.com/china/msdn/events/webcasts/shared/webcast/consyscourse/CsharpOOD.aspx

 

 

Observer

   1:  public interface IAccountObserver

   2:  {

   3:      void Upadate();

   4:  }

   5:   

   6:  public class ATM

   7:  {

   8:      BankAccount bankAccount;

   9:   

  10:      public void process()

  11:      {

  12:          bankAccount.Withdraw(data);

  13:      }

  14:  }

  15:   

  16:  public class BankAccount

  17:  {

  18:      ArrayList<IAccountObserver> observerList=new ArrayList<IAccountObserver>();

  19:   

  20:      public void Withdraw(int data)

  21:      {

  22:          //...

  23:   

  24:          userAccountArgs args=new 

  25:          foreach(IAccountObserver observer in observerList)

  26:          {

  27:              observer.Update(args);

  28:          }

  29:   

  30:      }

  31:   

  32:      public void AddObserver(IAccountObserver observer)

  33:      {

  34:          observerList.Add(observer);

  35:      }

  36:  }

  37:   

  38:  public class Emailer

  39:  {

  40:      public void SendEmail(string to)

  41:      {

  42:          //...

  43:      }

  44:  }

  45:   

  46:  public class Mobile

  47:  {

  48:      public void SendNotification(string phoneNumber)

  49:      {

  50:          //...

  51:      }

  52:  }

 

Observer Event

public delegate void AccountchangeEventhandler(

object sender, 

AccountChangeEventArgs args);



public class BankAccount

{

    public event AccountChangeEventHandler AccountChange;



    public void Withdraw(int data)

    {

        //...



        AccountChangeEventArgs args=new AccountChangeEventArgs();

        foreach(IAccountObserver observer in observerList)

        {

            observer.Update(args);

        }



    }



    protected virtual OnAccountChange()

    {

        if(AccountChange!=null)

        {

            AccountChange(args);

        }

    }

}



public class Emailer

{

    public void Update(object sender, UserAccountArgs args)

    {

        //...

    }

}



class App

{

    public static void Main()

    {

        BankAccount bankAccount=new BankAccount();



        Emailer emailer=new Emailer();

        bankAccount.AccountChange+=new AccountChangeEventHandler(emailer.Update)



        //...

        bankAccount.Withdraw(234);

    }

}