主旨 < T > .Subscribe 方法
訂閱主體的觀察者。
Namespace：System.Reactive.Subjects
裝配： System.Reactive.dll) 中的 System.Reactive (
語法
'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
參數
- 觀測 器
類型：System.IObserver<T>
要訂閱主體的觀察者。
傳回值
類型： System.IDisposable
IDisposable 物件，可用來取消訂閱主體的觀察者。
實作
IObservable < T > .訂閱 (IObserver < T >)
範例
此範例示範主旨類別的使用方式。 字串類型的 Subject 實例是用來訂閱兩個範例新聞摘要。 這些摘要只會以間隔發佈隨機新聞頭條，不超過五秒。 接著會針對主體的可觀察介面建立兩個訂用帳戶，以接收合併的資料流程。 一個訂用帳戶會將資料流程中的每個專案回報為「所有新聞」。 另一個訂用帳戶會篩選資料流程中的每個標題，只報告當地標題。 訂用帳戶都會寫入主控台視窗收到的每個標題。 當使用者按下 Enter 鍵並呼叫 Dispose 以取消這兩個訂用帳戶時，處理就會終止。
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)];
}
}
}
下列輸出是使用範例程式碼所產生。
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.
********************************** [ 本機新聞標題報告 ]**********************************摘要名稱：頭條新聞摘要 #1 標題：我們在您的區域中有一位成功者。
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.
********************************** [ 本機新聞標題報告 ]**********************************摘要名稱：頭條新聞摘要 #2 標題：您的區域中發生地震。