从订阅方法实现创建可观察序列。
Namespace：System.Reactive.Linq
装配： System.Reactive.dll) 中的 System.Reactive (
语法
'Declaration
Public Shared Function Create(Of TSource) ( _
subscribe As Func(Of IObserver(Of TSource), IDisposable) _
) As IObservable(Of TSource)
'Usage
Dim subscribe As Func(Of IObserver(Of TSource), IDisposable)
Dim returnValue As IObservable(Of TSource)
returnValue = Observable.Create(subscribe)
public static IObservable<TSource> Create<TSource>(
Func<IObserver<TSource>, IDisposable> subscribe
)
public:
generic<typename TSource>
static IObservable<TSource>^ Create(
Func<IObserver<TSource>^, IDisposable^>^ subscribe
)
static member Create :
subscribe:Func<IObserver<'TSource>, IDisposable> -> IObservable<'TSource>
JScript does not support generic types and methods.
类型参数
- TSource
源的类型。
parameters
- subscribe
类型： System.Func<IObserver<TSource>、 IDisposable>
生成的可观测序列的 subscribe 方法的实现。
返回值
类型： System.IObservable<TSource>
具有订阅方法的指定实现的可观测序列。
备注
Create 运算符允许你创建自己的自定义序列，而无需为序列完全实现 IObservable<T> 接口。 使用此运算符，只需实现一个订阅函数，该函数采用 IObserver<T> ，其中 T 是类型，并返回 IDisposable 接口，该接口用于通过调用 IDisposable：:D ispose () 取消订阅。 使用此运算符优先于 IObservable<T> 接口的手动实现。
示例
此示例模拟一个假设的票证系统，其中提供了可观测的票证序列，但未完全实现 IObservable<Ticket>。 TicketFactory 类实现其自己的订阅方法，称为 TicketSubscribe。 此方法作为 subscribe 参数传递给 Create 运算符。 TicketSubscribe 通过调用从 TicketSubscribe 返回的 IDisposable 接口上的 Dispose 方法，在另一个线程上创建一个连续的票证序列，直到取消订阅。 IObserver<票证> 传递到 TicketSubscribe。 序列中的每个票证都是通过调用 IObserver Ticket> 传递的<。OnNext () 。 为订阅执行的观察者操作会将每个票证显示到控制台窗口。
using System;
using System.Threading;
using System.Threading.Tasks;
using System.Reactive.Linq;
namespace Example
{
class Program
{
static void Main()
{
IObservable<Ticket> ticketObservable = Observable.Create((Func<IObserver<Ticket>, IDisposable>)TicketFactory.TicketSubscribe);
//*********************************************************************************//
//*** This is a sequence of tickets. Display each ticket in the console window. ***//
//*********************************************************************************//
using(IDisposable handle = ticketObservable.Subscribe(ticket => Console.WriteLine(ticket.ToString())))
{
Console.WriteLine("\nPress ENTER to unsubscribe...\n");
Console.ReadLine();
}
}
}
//***************************************************************************************************//
//*** ***//
//*** The Ticket class just represents a hypothetical ticket composed of an ID and a timestamp. ***//
//*** ***//
//***************************************************************************************************//
class Ticket
{
private readonly string ticketID;
private readonly DateTime timeStamp;
public Ticket(string tid)
{
ticketID = tid;
timeStamp = DateTime.Now;
}
public override string ToString()
{
return String.Format("Ticket ID : {0}\nTimestamp : {1}\n", ticketID, timeStamp.ToString());
}
}
//***************************************************************************************************//
//*** ***//
//*** The TicketFactory class generates a new sequence of tickets on a separate thread. The ***//
//*** generation of the sequence is initiated by the TicketSubscribe method which will be passed ***//
//*** to Observable.Create(). ***//
//*** ***//
//*** TicketSubscribe() provides the IDisposable interface used to dispose of the subscription ***//
//*** stopping ticket generation resources. ***//
//*** ***//
//***************************************************************************************************//
public class TicketFactory : IDisposable
{
private bool bGenerate = true;
internal TicketFactory(object ticketObserver)
{
//************************************************************************//
//*** The sequence generator for tickets will be run on another thread ***//
//************************************************************************//
Task.Factory.StartNew(new Action<object>(TicketGenerator), ticketObserver);
}
//**************************************************************************************************//
//*** Dispose frees the ticket generating resources by allowing the TicketGenerator to complete. ***//
//**************************************************************************************************//
public void Dispose()
{
bGenerate = false;
}
//*****************************************************************************************************************//
//*** TicketGenerator generates a new ticket every 3 sec and calls the observer's OnNext handler to deliver it. ***//
//*****************************************************************************************************************//
private void TicketGenerator(object observer)
{
IObserver<Ticket> ticketObserver = (IObserver<Ticket>)observer;
//***********************************************************************************************//
//*** Generate a new ticket every 3 sec and call the observer's OnNext handler to deliver it. ***//
//***********************************************************************************************//
Ticket t;
while (bGenerate)
{
t = new Ticket(Guid.NewGuid().ToString());
ticketObserver.OnNext(t);
Thread.Sleep(3000);
}
}
//********************************************************************************************************************************//
//*** TicketSubscribe starts the flow of tickets for the ticket sequence when a subscription is created. It is passed to ***//
//*** Observable.Create() as the subscribe parameter. Observable.Create() returns the IObservable<Ticket> that is used to ***//
//*** create subscriptions by calling the IObservable<Ticket>.Subscribe() method. ***//
//*** ***//
//*** The IDisposable interface returned by TicketSubscribe is returned from the IObservable<Ticket>.Subscribe() call. Calling ***//
//*** Dispose cancels the subscription freeing ticket generating resources. ***//
//********************************************************************************************************************************//
public static IDisposable TicketSubscribe(object ticketObserver)
{
TicketFactory tf = new TicketFactory(ticketObserver);
return tf;
}
}
}
下面是示例代码的示例输出。 按 Enter 取消注册。
Press ENTER to unsubscribe...
Ticket ID : a5715731-b9ba-4992-af00-d5030956cfc4
Timestamp : 5/18/2011 6:48:50 AM
Ticket ID : d9797b2b-a356-4928-bfce-797a1637b11d
Timestamp : 5/18/2011 6:48:53 AM
Ticket ID : bb01dc7d-1ed5-4ba0-9ce0-6029187792be
Timestamp : 5/18/2011 6:48:56 AM
Ticket ID : 0d3c95de-392f-4ed3-bbda-fed2c6bc7287
Timestamp : 5/18/2011 6:48:59 AM
Ticket ID : 4d19f79e-6d4f-4fec-83a8-9644a1d4e759
Timestamp : 5/18/2011 6:49:05 AM