much like the Linq to Whatever technologies enable different semantics from the same query. The composition can be represented as data and thus interpreted differently under different circumstance. Cold observables can lay idle until there is an appropriate subscription and then remain active only until the subscription (IObserver) is disposed of. monadic bindings enable the 'pure' chaining of observable sequences. This enables developers to compose observables together and apply linq style queries comprehensions over them lazily. IObservable has been added to allow RX to publish query comprehensions as extension methods to this interface, much like the original Linq operators did to IEnumerable. IObserver is the mathematical dual of IEnumerable and where as IEnumerable represents pull based notifications, IObservable represents push based. IObservable and IObserver have been added for the Reactive Extensions Framework. While I may very well agree with such a conclusion (to a certain extent), he fails to elaborate on the why and I believe this shows a lack of appreciation/understanding on his part as to the true value at hand. I'm not sure it's the authors intention, but he seems to suggest that it would be better to start hand coding observables and observers through these interfaces than to use the existing well understood event mechanism. The article is essentially a rehash of the MSDN documentation for IObservable, which does indeed profess the types to be an abstraction of the Observer pattern, but we already have familiar and well known implementations of this pattern in the form of multi cast delegates (events) so it is not the reason they were added to the BCL.
bit rude of me not to elaborate and help out a little. I hadn't realised the comment was added to the thread like that. As an example, we use a class which represents a location, which inherits from the Observable class. Also there is a method, which can be called to notify all observers that there are changes in the observed object. It returns an instance of the Unsubscriber class, which is a simple inner class that implements the IDisposable interface. It already implements the IObservable(T) and so contains the subscribe method. If (observer != null & observers.Contains(observer)) Public Unsubscriber(List> observers, IObserver observer) Return new Unsubscriber(observers, observer) Public IDisposable Subscribe(IObserver observer)
#IOBSERVE INTERNET EQUIVALENT CODE#
The following code shows a simple generic approach for such an observable base class.Ĭopy Code public class Observable: IObservableįoreach (IObserver observer in observers) Normally an observable can be implemented without any additional code (only the method call which indicates a change). This is something which isn't part of the base class library. But first we need a base class for all observables which separates the specific code from the standard observable code. I will show in a simple example how it works.
#IOBSERVE INTERNET EQUIVALENT UPDATE#
The observer has to implement three methods, OnCompleted which is called to indicate that the observable has finished sending notifications, OnError when an error occurred, and OnNext when new data is available (the method is also called update in other languages). It returns an object of the type IDisposable which can be used to unsubscribe by calling Dispose. The observable must implement the subscribe method where observers can be attached. IDisposable Subscribe(IObserver observer)
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