IObserver<T> Interface

Definition

푸시 기반 알림을 수신하기 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)

Type Parameters

T

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

This type parameter is contravariant. That is, you can use either the type you specified or any type that is less derived. For more information about covariance and contravariance, see Covariance and Contravariance in Generics.
Derived

Examples

다음 예제에서는 관찰자 디자인 패턴을 보여 줍니다.The following example illustrates the observer design pattern. 위도 및 경도 정보를 포함 하는 Location 클래스를 정의 합니다.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

LocationReporter 클래스는 IObserver<T> 구현을 제공 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 생성자에는 LocationReporter 인스턴스가 문자열 출력에서 자신을 식별할 수 있도록 하는 name 매개 변수가 포함 되어 있습니다.Its constructor includes a name parameter, which allows the LocationReporter instance to identify itself in its string output. 또한 공급자의 Subscribe 메서드에 대 한 호출을 래핑하는 Subscribe 메서드도 포함 되어 있습니다.It also includes a Subscribe method, which wraps a call to the provider's Subscribe method. 이렇게 하면 메서드가 반환 된 IDisposable 참조를 전용 변수에 할당할 수 있습니다.This enables the method to assign the returned IDisposable reference to a private variable. LocationReporter 클래스에는 IObservable<T>.Subscribe 메서드에서 반환 하는 개체의 IDisposable.Dispose 메서드를 호출 하는 Unsubscribe 메서드도 포함 되어 있습니다.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 LocationReporter 클래스를 정의 합니다.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

LocationTracker 클래스는 IObservable<T> 구현을 제공 합니다.The LocationTracker class provides the IObservable<T> implementation. 해당 TrackLocation 메서드에 위도 및 경도 데이터를 포함 하는 nullable Location 개체가 전달 되었습니다.Its TrackLocation method is passed a nullable Location object that contains the latitude and longitude data. Location 값이 null되지 않은 경우 TrackLocation 메서드는 각 관찰자의 OnNext 메서드를 호출 합니다.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

Location 값이 null경우 TrackLocation 메서드는 다음 예제와 같이 LocationNotFoundException 개체를 인스턴스화합니다.If the Location value is null, the TrackLocation method instantiates a LocationNotFoundException object, which is shown in the following example. 그런 다음 각 관찰자의 OnError 메서드를 호출 하 여 LocationNotFoundException 개체를 전달 합니다.It then calls each observer's OnError method and passes it the LocationNotFoundException object. LocationNotFoundExceptionException에서 파생 되지만 새 멤버를 추가 하지는 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

관찰자는 IObservable<T>.Subscribe 메서드를 호출 하 여 TrackLocation 개체에서 알림을 받도록 등록 하 고,이 메서드는 관찰자 개체에 대 한 참조를 전용 제네릭 List<T> 개체에 할당 합니다.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 관찰자가 알림 수신을 중지할 수 있도록 하는 IDisposable 구현인 Unsubscriber 개체를 반환 합니다.The method returns an Unsubscriber object, which is an IDisposable implementation that enables observers to stop receiving notifications. LocationTracker 클래스에는 EndTransmission 메서드도 포함 되어 있습니다.The LocationTracker class also includes an EndTransmission method. 추가 위치 데이터를 사용할 수 없는 경우 메서드는 각 관찰자의 OnCompleted 메서드를 호출한 다음 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.

Remarks

IObserver<T>IObservable<T> 인터페이스는 관찰자 디자인 패턴이 라고도 하는 푸시 기반 알림에 대 한 일반화 된 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. IObservable<T> 인터페이스는 알림을 보내는 클래스 (공급자)를 나타냅니다. IObserver<T> 인터페이스는이를 받는 클래스 (관찰자)를 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). T는 알림 정보를 제공 하는 클래스를 나타냅니다.T represents the class that provides the notification information.

IObserver<T> 구현은 공급자의 IObservable<T>.Subscribe 메서드에 자체 인스턴스를 전달 하 여 공급자 (IObservable<T> 구현)에서 알림을 받을 수 있도록 정렬 합니다.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 메서드는 공급자가 알림 전송을 완료 하기 전에 관찰자를 구독 취소 하는 데 사용할 수 있는 IDisposable 개체를 반환 합니다.This method returns an IDisposable object that can be used to unsubscribe the observer before the provider finishes sending notifications.

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

  • 관찰자에 게 새 데이터 또는 상태 정보를 제공 하기 위해 일반적으로 공급자가 호출 하는 OnNext 메서드입니다.The OnNext method, which is typically called by the provider to supply the observer with new data or state information.

  • 데이터를 사용할 수 없거나, 액세스할 수 없거나, 손상 되었거나, 공급자에 게 다른 오류 조건이 발생 했음을 나타내기 위해 일반적으로 공급자가 호출 하는 OnError 메서드입니다.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.

  • 공급자가 관찰자에 게 알림을 보내기 위해 일반적으로 호출 하는 OnCompleted 메서드입니다.The OnCompleted method, which is typically called by the provider to indicate that it has finished sending notifications to observers.

Methods

OnCompleted()

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

OnError(Exception)

공급자에게 오류 조건이 발생했다는 것을 관찰자에게 알립니다.Notifies the observer that the provider has experienced an error condition.

OnNext(T)

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

Applies to

See also