Objet<T>. Méthode Subscribe
Abonne un observateur au sujet.
Espace de noms :System.Reactive.Subjects
Assemblée: System.Reactive (en System.Reactive.dll)
Syntaxe
'Declaration
Public Function Subscribe ( _
observer As IObserver(Of T) _
) As IDisposable
'Usage
Dim instance As Subject
Dim observer As IObserver(Of T)
Dim returnValue As IDisposable
returnValue = instance.Subscribe(observer)
public IDisposable Subscribe(
IObserver<T> observer
)
public:
virtual IDisposable^ Subscribe(
IObserver<T>^ observer
) sealed
abstract Subscribe :
observer:IObserver<'T> -> IDisposable
override Subscribe :
observer:IObserver<'T> -> IDisposable
public final function Subscribe(
observer : IObserver<T>
) : IDisposable
Paramètres
- Observateur
Type : System.IObserver<T>
Observateur pour s’abonner au sujet.
Valeur de retour
Type : System.IDisposable
Objet IDisposable qui peut être utilisé pour désinscrire l’observateur de l’objet.
Implémente
IObservable<T>. Subscribe(IObserver<T>)
Exemples
Cet exemple illustre l’utilisation de la classe subject. Une instance d’un objet du type chaîne est utilisée pour s’abonner à deux exemples de flux d’actualités. Ces flux publient simplement des titres d’actualités aléatoires à un intervalle ne dépassant pas cinq secondes d’intervalle. Deux abonnements par rapport à l’interface observable du sujet sont ensuite créés pour recevoir le flux de données combiné. Un abonnement signale chaque élément du flux de données comme « toutes les actualités ». L’autre abonnement filtre chaque titre du flux pour signaler uniquement les titres locaux. Les abonnements écrivent tous deux chaque titre reçu dans la fenêtre de console. Le traitement se termine lorsque l’utilisateur appuie sur la touche Entrée et que Supprimer est appelé pour annuler les deux abonnements.
using System;
using System.Reactive.Linq;
using System.Reactive.Subjects;
using System.Reactive.Concurrency;
using System.Threading;
namespace Example
{
class Program
{
static void Main()
{
//*****************************************************************************************************//
//*** ***//
//*** A subject acts similar to a proxy in that it acts as both a subscriber and a publisher ***//
//*** It's IObserver interface can be used to subscribe to multiple streams or sequences of data. ***//
//*** The data is then published through it's IObservable interface. ***//
//*** ***//
//*** In this example a simple string based subject is used to subscribe to multiple news feeds ***//
//*** that provide random news headlines. Subscribers can then subscribe to the subject's ***//
//*** observable interface to observe the data stream(s) or a subset ofthe stream(s). Below we ***//
//*** subscribe the subject to two different news headline feeds. Then two subscriptions are ***//
//*** created: one for delivery of all news headlines, the other receives only local news headlines ***//
//*** ***//
//*** A local news headline just contains the newsLocation substring ("in your area."). ***//
//*** ***//
//*****************************************************************************************************//
Subject<string> mySubject = new Subject<string>();
//*********************************************************//
//*** Create news feed #1 and subscribe mySubject to it ***//
//*********************************************************//
NewsHeadlineFeed NewsFeed1 = new NewsHeadlineFeed("Headline News Feed #1");
NewsFeed1.HeadlineFeed.Subscribe(mySubject);
//*********************************************************//
//*** Create news feed #2 and subscribe mySubject to it ***//
//*********************************************************//
NewsHeadlineFeed NewsFeed2 = new NewsHeadlineFeed("Headline News Feed #2");
NewsFeed2.HeadlineFeed.Subscribe(mySubject);
Console.WriteLine("Subscribing to news headline feeds.\n\nPress ENTER to exit.\n");
//*****************************************************************************************************//
//*** Create a subscription to the subject's observable sequence. This subscription will receive ***//
//*** all headlines. ***//
//*****************************************************************************************************//
IDisposable allNewsSubscription = mySubject.Subscribe(x =>
{
Console.WriteLine("Subscription : All news subscription\n{0}\n", x);
});
//*****************************************************************************************************//
//*** Create a subscription to the subject's observable sequence. This subscription will filter for ***//
//*** only local headlines. ***//
//*****************************************************************************************************//
IDisposable localNewsSubscription = mySubject.Where(x => x.Contains("in your area.")).Subscribe(x =>
{
Console.WriteLine("\n************************************\n" +
"***[ Local news headline report ]***\n" +
"************************************\n{0}\n\n", x);
});
Console.ReadLine();
//*********************************//
//*** Cancel both subscriptions ***//
//*********************************//
allNewsSubscription.Dispose();
localNewsSubscription.Dispose();
}
}
//*********************************************************************************//
//*** The NewsHeadlineFeed class is just a mock news feed in the form of an ***//
//*** observable sequence in Reactive Extensions. ***//
//*********************************************************************************//
class NewsHeadlineFeed
{
private string feedName; // Feedname used to label the stream
private IObservable<string> headlineFeed; // The actual data stream
private readonly Random rand = new Random(); // Used to stream random headlines.
//*** A list of predefined news events to combine with a simple location string ***//
static readonly string[] newsEvents = { "A tornado occurred ",
"Weather watch for snow storm issued ",
"A robbery occurred ",
"We have a lottery winner ",
"An earthquake occurred ",
"Severe automobile accident "};
//*** A list of predefined location strings to combine with a news event. ***//
static readonly string[] newsLocations = { "in your area.",
"in Dallas, Texas.",
"somewhere in Iraq.",
"Lincolnton, North Carolina",
"Redmond, Washington"};
public IObservable<string> HeadlineFeed
{
get { return headlineFeed; }
}
public NewsHeadlineFeed(string name)
{
feedName = name;
//*****************************************************************************************//
//*** Using the Generate operator to generate a continous stream of headline that occur ***//
//*** randomly within 5 seconds. ***//
//*****************************************************************************************//
headlineFeed = Observable.Generate(RandNewsEvent(),
evt => true,
evt => RandNewsEvent(),
evt => { Thread.Sleep(rand.Next(5000)); return evt; },
Scheduler.ThreadPool);
}
//****************************************************************//
//*** Some very simple formatting of the headline event string ***//
//****************************************************************//
private string RandNewsEvent()
{
return "Feedname : " + feedName + "\nHeadline : " + newsEvents[rand.Next(newsEvents.Length)] +
newsLocations[rand.Next(newsLocations.Length)];
}
}
}
La sortie suivante a été générée avec l’exemple de code.
Subscribing to news headline feeds.
Press ENTER to exit.
Subscription : All news subscription
Feedname : Headline News Feed #2
Headline : A robbery occurred somewhere in Iraq.
Subscription : All news subscription
Feedname : Headline News Feed #2
Headline : An earthquake occurred in Dallas, Texas.
Subscription : All news subscription
Feedname : Headline News Feed #1
Headline : We have a lottery winner in your area.
********************************** [ Bulletin d’actualités locales ]********************************** Feedname : Flux d’actualités de titre #1 Titre : Nous avons un gagnant de loterie dans votre région.
Subscription : All news subscription
Feedname : Headline News Feed #2
Headline : Severe automobile accident Redmond, Washington
Subscription : All news subscription
Feedname : Headline News Feed #2
Headline : We have a lottery winner in Dallas, Texas.
Subscription : All news subscription
Feedname : Headline News Feed #2
Headline : An earthquake occurred in Dallas, Texas.
Subscription : All news subscription
Feedname : Headline News Feed #1
Headline : We have a lottery winner somewhere in Iraq.
Subscription : All news subscription
Feedname : Headline News Feed #2
Headline : Severe automobile accident somewhere in Iraq.
Subscription : All news subscription
Feedname : Headline News Feed #2
Headline : An earthquake occurred in your area.
********************************** [ Bulletin d’actualités locales ]********************************** Feedname : Flux d’actualités en titre #2 Titre : Un tremblement de terre s’est produit dans votre région.