IObservable<T> IObservable<T> IObservable<T> IObservable<T> Interface


プッシュ ベースの通知用プロバイダーを定義します。Defines a provider for push-based notification.

generic <typename T>
public interface class IObservable
public interface IObservable<out T>
type IObservable<'T> = interface
Public Interface IObservable(Of Out T)



通知情報を提供するオブジェクト。The object that provides notification information.


次の例は、オブザーバー デザイン パターンを示しています。The following example illustrates the observer design pattern. 定義、Location緯度と経度の情報を含むクラスです。It defines a Location class that contains latitude and longitude information.

public struct Location
   double lat, lon;

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

   public double Latitude
   { get { return; } }

   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) = latitude
      Me.lon = longitude
   End Sub

   Public ReadOnly Property Latitude As Double
      End Get
   End Property

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

LocationTrackerクラスには、IObservable<T>実装します。The LocationTracker class provides the IObservable<T> implementation. そのTrackLocationメソッドは、null 許容型で渡されるLocation緯度と経度のデータを格納しているオブジェクト。Its TrackLocation method is passed a nullable Location object that contains the latitude and longitude data. 場合、Location値がnullTrackLocationメソッドの呼び出し、OnNext各オブザーバーのメソッド。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)) 
      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))

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

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

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
      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
         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())
         End If
   End Sub

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

場合、Location値はnullTrackLocationメソッドをインスタンス化、LocationUnknownExceptionオブジェクトで、次の例に示します。If the Location value is null, the TrackLocation method instantiates a LocationUnknownException object, which is shown in the following example. 各オブザーバーを呼び出してOnErrorメソッドを渡します、LocationUnknownExceptionオブジェクト。It then calls each observer's OnError method and passes it the LocationUnknownException object. なおLocationUnknownExceptionから派生したException、新しいメンバーを追加しません。Note that LocationUnknownException 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

通知を受信するオブザーバーを登録、TrackLocationオブジェクトを呼び出すことによってそのIObservable<T>.Subscribeメソッドで、オブザーバー オブジェクトへの参照をプライベート ジェネリックに割り当てますList<T>オブジェクト。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. メソッドを返します、Unsubscriberとなるオブジェクト、IDisposableにより、通知の受信を停止するオブザーバーを実装します。The method returns an Unsubscriber object, which is an IDisposable implementation that enables observers to stop receiving notifications. LocationTrackerクラスも含まれています、EndTransmissionメソッド。The LocationTracker class also includes an EndTransmission method. 場所データをさらに利用できない場合は、メソッドの各オブザーバーのOnCompletedメソッドし、オブザーバーの内部リストをクリアします。When no further location data is available, the method calls each observer's OnCompleted method and then clears the internal list of observers.

この例で、LocationReporterクラスには、IObserver<T>実装します。In this example, the LocationReporter class provides the IObserver<T> implementation. コンソールには、現在の場所に関する情報が表示されます。It displays information about the current location to the console. そのコンス トラクターが含まれています、nameパラメーターは、これにより、LocationReporterの文字列の出力で自身を識別するインスタンス。Its constructor includes a name parameter, which enables the LocationReporter instance to identify itself in its string output. 含まれています、Subscribeメソッドは、プロバイダーの呼び出しをラップするSubscribeメソッド。It also includes a Subscribe method, which wraps a call to the provider's Subscribe method. これにより、メソッドは、返された割り当てるIDisposable秘密の変数への参照。This allows the method to assign the returned IDisposable reference to a private variable. LocationReporterクラスも含まれています、Unsubscribeメソッドを呼び出す、IDisposable.Disposeによって返されるオブジェクトのメソッド、IObservable<T>.Subscribeメソッド。The LocationReporter class also includes an Unsubscribe method, which calls the IDisposable.Dispose method of the object that is returned by the IObservable<T>.Subscribe method. 次のコード定義、LocationReporterクラス。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);

   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()
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
         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)
   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()
   End Sub
End Class

次のコードは、プロバイダーとオブザーバーにし、インスタンス化します。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");
      LocationReporter reporter2 = new LocationReporter("MobileGPS");

      provider.TrackLocation(new Location(47.6456, -122.1312));
      provider.TrackLocation(new Location(47.6677, -122.1199));
// 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")
      Dim reporter2 As New LocationReporter("MobileGPS")

      provider.TrackLocation(New Location(47.6456, -122.1312))
      provider.TrackLocation(New Location(47.6677, -122.1199))
   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.


IObserver<T>IObservable<T>インターフェイスが汎用化されたプッシュ ベースの通知、オブザーバー デザイン パターンとも呼ばれるメカニズムを提供します。The IObserver<T> and IObservable<T> interfaces provide a generalized mechanism for push-based notification, also known as the observer design pattern. IObservable<T>インターフェイス (プロバイダー); の通知を送信するクラスを表す、IObserver<T>インターフェイスは、受信する (オブザーバー) クラスを表します。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 通知情報を提供するクラスを表します。T represents the class that provides the notification information. 一部のプッシュ ベースの通知で、IObserver<T>実装とT同じ型を表すことができます。In some push-based notifications, the IObserver<T> implementation and T can represent the same type.

プロバイダーは、1 つのメソッドを実装する必要がありますSubscribeオブザーバーがプッシュ ベースの通知を受信することを示します。The provider must implement a single method, Subscribe, that indicates that an observer wants to receive push-based notifications. メソッドの呼び出し元は、オブザーバーのインスタンスを渡します。Callers to the method pass an instance of the observer. メソッドを返します、IDisposableにより、プロバイダーが送信を停止する前に、いつでも通知をキャンセルするオブザーバーを実装します。The method returns an IDisposable implementation that enables observers to cancel notifications at any time before the provider has stopped sending them.

任意の時点では、指定されたプロバイダーは 0、1、または複数のオブザーバーがあります。At any given time, a given provider may have zero, one, or multiple observers. プロバイダーは、オブザーバーへの参照を格納すると、それらが有効である通知を送信することを確認します。The provider is responsible for storing references to observers and ensuring that they are valid before it sends notifications. IObservable<T>インターフェイスはオブザーバーまたは通知が送信される注文の数に関するどのような想定を行いません。The IObservable<T> interface does not make any assumptions about the number of observers or the order in which notifications are sent.

プロバイダーは、呼び出すことによって、オブザーバーに次の 3 種類の通知を送信IObserver<T>メソッド。The provider sends the following three kinds of notifications to the observer by calling IObserver<T> methods:

  • 現在のデータ。The current data. プロバイダーが呼び出すことができます、IObserver<T>.OnNextオブザーバーを渡すメソッドをTを現在のデータや変更されたデータは、新しいデータを持つオブジェクト。The provider can call the IObserver<T>.OnNext method to pass the observer a T object that has current data, changed data, or fresh data.

  • エラー条件。An error condition. プロバイダーが呼び出すことができます、IObserver<T>.OnError何らかのエラー状態が発生したことをオブザーバーに通知するメソッド。The provider can call the IObserver<T>.OnError method to notify the observer that some error condition has occurred.

  • さらにデータがありません。No further data. プロバイダーが呼び出すことができます、IObserver<T>.OnCompleted通知の送信が完了したことをオブザーバーに通知するメソッド。The provider can call the IObserver<T>.OnCompleted method to notify the observer that it has finished sending notifications.


Subscribe(IObserver<T>) Subscribe(IObserver<T>) Subscribe(IObserver<T>) Subscribe(IObserver<T>)

オブザーバーが通知を受け取ることをプロバイダーに通知します。Notifies the provider that an observer is to receive notifications.