IObserver<T> 인터페이스

정의

푸시 기반 알림을 받기 위한 메커니즘을 제공합니다.Provides a mechanism for receiving push-based notifications.

generic <typename T>
public interface class IObserver
public interface IObserver<in T>
type IObserver<'T> = interface
Public Interface IObserver(Of In T)

형식 매개 변수

T

알림 정보를 제공하는 개체입니다.The object that provides notification information.

파생

예제

다음 예제에서는 관찰자 디자인 패턴을 보여 줍니다.The following example illustrates the observer design pattern. 정의 Location 위도 및 경도 정보를 포함 하는 클래스입니다.It defines a Location class that contains latitude and longitude information.

public struct Location
{
   double lat, lon;

   public Location(double latitude, double longitude)
   {
      this.lat = latitude;
      this.lon = longitude;
   }

   public double Latitude
   { get { return this.lat; } }

   public double Longitude
   { get { return this.lon; } }
}
Public Structure Location
   Dim lat, lon As Double

   Public Sub New(ByVal latitude As Double, ByVal longitude As Double)
      Me.lat = latitude
      Me.lon = longitude
   End Sub

   Public ReadOnly Property Latitude As Double
      Get
         Return Me.lat
      End Get
   End Property

   Public ReadOnly Property Longitude As Double
      Get
         Return Me.lon
      End Get
   End Property
End Structure

합니다 LocationReporter 클래스를 제공 합니다 IObserver<T> 구현 합니다.The LocationReporter class provides the IObserver<T> implementation. 현재 위치에 대 한 정보를 콘솔에 표시 됩니다.It displays information about the current location to the console. 해당 생성자를 포함 한 name 매개 변수를를 LocationReporter 문자열 출력에서 자신을 식별 하는 인스턴스.Its constructor includes a name parameter, which allows the LocationReporter instance to identify itself in its string output. 또한를 Subscribe 메서드는 공급자에 대 한 호출을 래핑하는 Subscribe 메서드.It also includes a Subscribe method, which wraps a call to the provider's Subscribe method. 이렇게 하면 반환 된 방법 IDisposable private 변수를 참조 합니다.This enables the method to assign the returned IDisposable reference to a private variable. LocationReporter 클래스도 포함 되어 있습니다를 Unsubscribe 메서드를 호출 하는 합니다 IDisposable.Dispose 반환 하는 개체의 메서드는 IObservable<T>.Subscribe 메서드.The LocationReporter class also includes an Unsubscribe method, which calls the IDisposable.Dispose method of the object returned by the IObservable<T>.Subscribe method. 다음 코드는 정의 된 LocationReporter 클래스입니다.The following code defines the LocationReporter class.

using System;

public class LocationReporter : IObserver<Location>
{
   private IDisposable unsubscriber;
   private string instName;

   public LocationReporter(string name)
   {
      this.instName = name;
   }

   public string Name
   {  get{ return this.instName; } }

   public virtual void Subscribe(IObservable<Location> provider)
   {
      if (provider != null) 
         unsubscriber = provider.Subscribe(this);
   }

   public virtual void OnCompleted()
   {
      Console.WriteLine("The Location Tracker has completed transmitting data to {0}.", this.Name);
      this.Unsubscribe();
   }

   public virtual void OnError(Exception e)
   {
      Console.WriteLine("{0}: The location cannot be determined.", this.Name);
   }

   public virtual void OnNext(Location value)
   {
      Console.WriteLine("{2}: The current location is {0}, {1}", value.Latitude, value.Longitude, this.Name);
   }

   public virtual void Unsubscribe()
   {
      unsubscriber.Dispose();
   }
}
Public Class LocationReporter : Implements IObserver(Of Location)
   Dim unsubscriber As IDisposable
   Dim instName As String

   Public Sub New(ByVal name As String)
      Me.instName = name
   End Sub

   Public ReadOnly Property Name As String
      Get
         Return instName
      End Get
   End Property

   Public Overridable Sub Subscribe(ByVal provider As IObservable(Of Location))
      If provider Is Nothing Then Exit Sub
      unsubscriber = provider.Subscribe(Me)
   End Sub

   Public Overridable Sub OnCompleted() Implements System.IObserver(Of Location).OnCompleted
      Console.WriteLine("The Location Tracker has completed transmitting data to {0}.", Me.Name)
      Me.Unsubscribe()
   End Sub

   Public Overridable Sub OnError(ByVal e As System.Exception) Implements System.IObserver(Of Location).OnError
      Console.WriteLine("{0}: The location cannot be determined.", Me.Name)
   End Sub

   Public Overridable Sub OnNext(ByVal value As Location) Implements System.IObserver(Of Location).OnNext
      Console.WriteLine("{2}: The current location is {0}, {1}", value.Latitude, value.Longitude, Me.Name)
   End Sub

   Public Overridable Sub Unsubscribe()
      unsubscriber.Dispose()
   End Sub
End Class

합니다 LocationTracker 클래스를 제공 합니다 IObservable<T> 구현 합니다.The LocationTracker class provides the IObservable<T> implementation. 해당 TrackLocation 메서드는 null을 허용 되는지를 Location 위도 및 경도 데이터가 들어 있는 개체입니다.Its TrackLocation method is passed a nullable Location object that contains the latitude and longitude data. 경우는 Location 값이 아닙니다 nullTrackLocation 메서드 호출을 OnNext 각 관찰자의 메서드.If the Location value is not null, the TrackLocation method calls the OnNext method of each observer.

public class LocationTracker : IObservable<Location>
{
   public LocationTracker()
   {
      observers = new List<IObserver<Location>>();
   }

   private List<IObserver<Location>> observers;

   public IDisposable Subscribe(IObserver<Location> observer) 
   {
      if (! observers.Contains(observer)) 
         observers.Add(observer);
      return new Unsubscriber(observers, observer);
   }

   private class Unsubscriber : IDisposable
   {
      private List<IObserver<Location>>_observers;
      private IObserver<Location> _observer;

      public Unsubscriber(List<IObserver<Location>> observers, IObserver<Location> observer)
      {
         this._observers = observers;
         this._observer = observer;
      }

      public void Dispose()
      {
         if (_observer != null && _observers.Contains(_observer))
            _observers.Remove(_observer);
      }
   }

   public void TrackLocation(Nullable<Location> loc)
   {
      foreach (var observer in observers) {
         if (! loc.HasValue)
            observer.OnError(new LocationUnknownException());
         else
            observer.OnNext(loc.Value);
      }
   }

   public void EndTransmission()
   {
      foreach (var observer in observers.ToArray())
         if (observers.Contains(observer))
            observer.OnCompleted();

      observers.Clear();
   }
}
Public Class LocationTracker : Implements IObservable(Of Location)

   Public Sub New()
      observers = New List(Of IObserver(Of Location))
   End Sub

   Private observers As List(Of IObserver(Of Location))

   Public Function Subscribe(ByVal observer As System.IObserver(Of Location)) As System.IDisposable _
                            Implements System.IObservable(Of Location).Subscribe
      If Not observers.Contains(observer) Then
         observers.Add(observer)
      End If
      Return New Unsubscriber(observers, observer)
   End Function

   Private Class Unsubscriber : Implements IDisposable
      Private _observers As List(Of IObserver(Of Location))
      Private _observer As IObserver(Of Location)

      Public Sub New(ByVal observers As List(Of IObserver(Of Location)), ByVal observer As IObserver(Of Location))
         Me._observers = observers
         Me._observer = observer
      End Sub

      Public Sub Dispose() Implements IDisposable.Dispose
         If _observer IsNot Nothing AndAlso _observers.Contains(_observer) Then
            _observers.Remove(_observer)
         End If
      End Sub
   End Class

   Public Sub TrackLocation(ByVal loc As Nullable(Of Location))
      For Each observer In observers
         If Not loc.HasValue Then
            observer.OnError(New LocationUnknownException())
         Else
            observer.OnNext(loc.Value)
         End If
      Next
   End Sub

   Public Sub EndTransmission()
      For Each observer In observers.ToArray()
         If observers.Contains(observer) Then observer.OnCompleted()
      Next
      observers.Clear()
   End Sub
End Class

경우는 Location 값이 null, TrackLocation 메서드를 만드는 데는 LocationNotFoundException 다음 예제에 나와 있는 개체입니다.If the Location value is null, the TrackLocation method instantiates a LocationNotFoundException object, which is shown in the following example. 그런 다음 각 관찰자를 호출 OnError 메서드를 전달 합니다 LocationNotFoundException 개체.It then calls each observer's OnError method and passes it the LocationNotFoundException object. 사실은 LocationNotFoundException 에서 파생 Exception 하지만 새 멤버를 추가 하지 않습니다.Note that LocationNotFoundException derives from Exception but does not add any new members.

public class LocationUnknownException : Exception
{
   internal LocationUnknownException() 
   { }
}
Public Class LocationUnknownException : Inherits Exception
   Friend Sub New()
   End Sub
End Class

관찰자에서 알림을 받으려면 등록을 TrackLocation 개체를 호출 하 여 해당 IObservable<T>.Subscribe private 제네릭 observer 개체에 대 한 참조를 할당 하는 메서드를 List<T> 개체입니다.Observers register to receive notifications from a TrackLocation object by calling its IObservable<T>.Subscribe method, which assigns a reference to the observer object to a private generic List<T> object. 메서드는 Unsubscriber 개체 이며는 IDisposable 관찰자가 알림 수신을 중지할 수 있도록 구현 합니다.The method returns an Unsubscriber object, which is an IDisposable implementation that enables observers to stop receiving notifications. 합니다 LocationTracker 클래스도 포함 되어 있습니다를 EndTransmission 메서드.The LocationTracker class also includes an EndTransmission method. 메서드 호출 된 각 관찰자의 추가 위치 데이터가 없음을 사용할 수 있는 경우 OnCompleted 메서드 관찰자의 내부 목록을 지웁니다.When no further location data is available, the method calls each observer's OnCompleted method and then clears the internal list of observers.

다음 코드는 다음 공급자와 관찰자를 인스턴스화합니다.The following code then instantiates the provider and the observer.

using System;

class Program
{
   static void Main(string[] args)
   {
      // Define a provider and two observers.
      LocationTracker provider = new LocationTracker();
      LocationReporter reporter1 = new LocationReporter("FixedGPS");
      reporter1.Subscribe(provider);
      LocationReporter reporter2 = new LocationReporter("MobileGPS");
      reporter2.Subscribe(provider);

      provider.TrackLocation(new Location(47.6456, -122.1312));
      reporter1.Unsubscribe();
      provider.TrackLocation(new Location(47.6677, -122.1199));
      provider.TrackLocation(null);
      provider.EndTransmission();
   }
}
// The example displays output similar to the following:
//      FixedGPS: The current location is 47.6456, -122.1312
//      MobileGPS: The current location is 47.6456, -122.1312
//      MobileGPS: The current location is 47.6677, -122.1199
//      MobileGPS: The location cannot be determined.
//      The Location Tracker has completed transmitting data to MobileGPS.
Module Module1
   Dim provider As LocationTracker

   Sub Main()
      ' Define a provider and two observers.
      provider = New LocationTracker()
      Dim reporter1 As New LocationReporter("FixedGPS")
      reporter1.Subscribe(provider)
      Dim reporter2 As New LocationReporter("MobileGPS")
      reporter2.Subscribe(provider)

      provider.TrackLocation(New Location(47.6456, -122.1312))
      reporter1.Unsubscribe()
      provider.TrackLocation(New Location(47.6677, -122.1199))
      provider.TrackLocation(Nothing)
      provider.EndTransmission()
   End Sub
End Module
' The example displays output similar to the following:
'       FixedGPS: The current location is 47.6456, -122.1312
'       MobileGPS: The current location is 47.6456, -122.1312
'       MobileGPS: The current location is 47.6677, -122.1199
'       MobileGPS: The location cannot be determined.
'       The Location Tracker has completed transmitting data to MobileGPS.

설명

합니다 IObserver<T>IObservable<T> 인터페이스 푸시 기반 알림의 경우 관찰자 디자인 패턴 라고도 일반화 메커니즘을 제공 합니다.The IObserver<T> and IObservable<T> interfaces provide a generalized mechanism for push-based notification, also known as the observer design pattern. 합니다 IObservable<T> 인터페이스 (공급자); 알림을 전송 하는 클래스를 나타냅니다는 IObserver<T> 인터페이스를 수신 합니다 (관찰자)는 클래스를 나타냅니다.The IObservable<T> interface represents the class that sends notifications (the provider); the IObserver<T> interface represents the class that receives them (the observer). T 알림 정보를 제공 하는 클래스를 나타냅니다.T represents the class that provides the notification information.

IObserver<T> 구현 공급자 로부터 알림을 수신 하도록 정렬 (을 IObservable<T> 구현)를 공급자의 자체 인스턴스를 전달 하 여 IObservable<T>.Subscribe 메서드.An IObserver<T> implementation arranges to receive notifications from a provider (an IObservable<T> implementation) by passing an instance of itself to the provider's IObservable<T>.Subscribe method. 이 메서드가 반환을 IDisposable 공급자 하기 전에 관찰자를 구독 취소를 사용할 수 있는 개체가 완료 알림을 전송 합니다.This method returns an IDisposable object that can be used to unsubscribe the observer before the provider finishes sending notifications.

IObserver<T> 인터페이스 관찰자 구현 해야 하는 다음 세 가지 메서드를 정의 합니다.The IObserver<T> interface defines the following three methods that the observer must implement:

  • OnNext 메서드는 일반적으로 공급자는 관찰자에 게 새 데이터 또는 상태 정보를 제공 하 여 호출 합니다.The OnNext method, which is typically called by the provider to supply the observer with new data or state information.

  • OnError 일반적으로 공급자에 액세스할 수 없거나 손상 된 데이터 임을 나타내려면에 의해 호출 되는 메서드 또는 공급자에 일부 오류 조건이 발생 했습니다.The OnError method, which is typically called by the provider to indicate that data is unavailable, inaccessible, or corrupted, or that the provider has experienced some other error condition.

  • OnCompleted 메서드는 일반적으로 관찰자가 알림 보내기를 완료 했음을 나타내기 위해 공급자에 의해 호출 됩니다.The OnCompleted method, which is typically called by the provider to indicate that it has finished sending notifications to observers.

메서드

OnCompleted()

공급자가 푸시 기반 알림 전송을 완료했음을 관찰자에게 알립니다.Notifies the observer that the provider has finished sending push-based notifications.

OnError(Exception)

공급자에 오류 조건이 있음을 옵서버에 알립니다.Notifies the observer that the provider has experienced an error condition.

OnNext(T)

관찰자에게 새 데이터를 제공합니다.Provides the observer with new data.

적용 대상

추가 정보