Observer Mode

Suppose there is a software company that notifies some customers of the information whenever a new product is launched.

 

Abstract The notification action into an interface.

Public interface IService

    {

Void Notif ();

    }

 

If you want to receive notifications, you need to implement the above interfaces. The customer here is seen as the Observer.

Public class CustomerA: IService

    {       

Public void Notif ()

        {

Console. WriteLine ("customer A has received A notification ~~ ");

        }

    }

Public class CustomerB: IService

    {

Public void Notif ()

        {

Console. WriteLine ("Customer B has received a notification ~~ ");

        }

    }

 

As a software company, it maintains a collection of customers and provides methods for registering and canceling registration to add or delete customers to the collection. Whenever there is a notification, we traverse the customer set and let IService execute the notification. A software company can be seen as an observed object, or as the source of initiating an action.

Public class MyCompany

    {

Private IList <IService> subscribers = new List <IService> ();

Public void Subscribe (IService subscriber)

        {

Subscribers. Add (subscriber );

        }

Public void CancelSubscribe (IService subscriber)

        {

Subscribers. Remove (subscriber );

        }

Public void SendMsg ()

        {

Foreach (IService service in subscribers)

            {

Service. Notif ();

            }

        }

    }

 

The client creates software company instances, creates observer instances, registers or cancels observers, and so on.

Class Program

    {

Static void Main (string [] args)

        {

MyCompany company = new MyCompany ();

IService customerA = new CustomerA ();

IService customerB = new CustomerB ();

Company. Subscribe (customerA );

Company. Subscribe (customerB );

Company. SendMsg ();

Console. ReadKey ();

        }

    }

 

 

Summary:

● Abstract the action of a notification into an interface
● If the observer wants to receive the notification, the notification interface is implemented.
● The observed object performs three tasks: maintaining the set of observers, registering/canceling the observer, and initiating an action to traverse the Observer set so that the notification interface can do the same thing.

Observer Mode