IObserver<T> IObserver<T> IObserver<T> IObserver<T> Interface

定義

プッシュ ベースの通知を受信するメカニズムを定義します。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)

型パラメーター

T

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

派生

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)
   {
      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クラスには、IObserver<T>実装します。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 allows 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 enables 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メソッドによって返されるオブジェクトのIObservable<T>.Subscribeメソッド。The LocationReporter class also includes an Unsubscribe method, which calls the IDisposable.Dispose method of the object 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);
      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)) 
         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

場合、Location値はnullTrackLocationメソッドをインスタンス化、LocationNotFoundException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 LocationNotFoundException 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、LocationNotFoundExceptionオブジェクト。It then calls each observer's OnError method and passes it the LocationNotFoundException object. なおLocationNotFoundExceptionから派生したExceptionが新しいメンバーは追加されません。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

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.

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");
      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.

注釈

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.

IObserver<T>プロバイダーから通知を受け取る実装を整列します (、IObservable<T>実装) をプロバイダーのそれ自体のインスタンスを渡すことによってIObservable<T>.Subscribeメソッド。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. このメソッドが戻る、IDisposableプロバイダーの前にオブザーバーをアンサブスク ライブするために使用できるオブジェクトは、通知の送信が完了するとします。This method returns an IDisposable object that can be used to unsubscribe the observer before the provider finishes sending notifications.

IObserver<T>インターフェイスはオブザーバーを実装する必要がある次の 3 つのメソッドを定義します。The IObserver<T> interface defines the following three methods that the observer must implement:

  • OnNextメソッドで、新しいデータまたは状態情報をオブザーバーに提供する、プロバイダーによって呼び出されます。The OnNext method, which is typically called by the provider to supply the observer with new data or state information.

  • OnErrorメソッドでは、データが利用不可、アクセスできない、または破損していることを示すために、プロバイダーによって通常と呼ばれる、またはプロバイダーには、その他の何らかのエラー状態が発生しました。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メソッドで、オブザーバーに通知の送信が完了したことを示す、プロバイダーによって呼び出されます。The OnCompleted method, which is typically called by the provider to indicate that it has finished sending notifications to observers.

メソッド

OnCompleted() OnCompleted() OnCompleted() OnCompleted()

プロバイダーでプッシュ ベースの通知の送信が完了したことをオブザーバーに通知します。Notifies the observer that the provider has finished sending push-based notifications.

OnError(Exception) OnError(Exception) OnError(Exception) OnError(Exception)

プロバイダーでエラー状態が発生したことをオブザーバーに通知します。Notifies the observer that the provider has experienced an error condition.

OnNext(T) OnNext(T) OnNext(T) OnNext(T)

新しいデータをオブザーバーに提供します。Provides the observer with new data.

適用対象

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