Extensiones reactivas (Rx) y la clase asíncrona

Question

He leído en este post: " la alegría de Rx: el modelo asincrónico basado en eventos vs IObservable " que el uso de EBAP se desanime. ¿Cuál es la mejor manera de diseñar un componente asíncrono con las nuevas extensiones Rx (algo así como el ejemplo de MSDN PrimeNumberCalculator)?

Gracias de antemano.

Actualizar Me las arreglé para escribir mi propia calculadora número primo, me gustaría escuchar sus opiniones:

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Threading;

namespace ConsoleApplication13
{
    public class PrimeNumberCalculator
    {
        private readonly Subject<int> primeSubject;
        private IDisposable currentSubscription;

        public PrimeNumberCalculator()
        {
            primeSubject = new Subject<int>();
            Primes = primeSubject.Hide();
        }

        public IObservable<int> Primes{ get; private set; }

        /// <summary>
        /// Determine if n is prime.
        /// </summary>
        private static bool IsPrime(ArrayList primes, int n, out int firstDivisor)
        {
            bool foundDivisor = false;
            bool exceedsSquareRoot = false;

            int i = 0;
            firstDivisor = 1;

            // Stop the search if:
            // there are no more primes in the list,
            // there is a divisor of n in the list, or
            // there is a prime that is larger than 
            // the square root of n.
            while ( (i < primes.Count) && !foundDivisor && !exceedsSquareRoot)
            {
                // The divisor variable will be the smallest 
                // prime number not yet tried.
                int divisor = (int)primes[i++];

                // Determine whether the divisor is greater
                // than the square root of n.
                if (divisor * divisor > n)
                {
                    exceedsSquareRoot = true;
                }
                // Determine whether the divisor is a factor of n.
                else if (n % divisor == 0)
                {
                    firstDivisor = divisor;
                    foundDivisor = true;
                }
            }

            return !foundDivisor;
        }

        /// <summary>
        /// Itereates from 1 to numberToTest and returns all primes.
        /// </summary>
        private IEnumerable<int> PrimeNumberIterator(int numberToTest)
        {
            var primes = new ArrayList();
            var n = 5;

            // Add the first prime numbers.
            primes.Add(2);
            primes.Add(3);

            // Do the work.
            while (n < numberToTest)
            {
                int firstDivisor;
                if (IsPrime(primes, n, out firstDivisor))
                {
                    // Report to the client that a prime was found.
                    yield return n;

                    Thread.Sleep(5000); //simulate long running task.
                    primes.Add(n);

                }
                // Skip even numbers.
                n += 2;
            }
        }

        /// <summary>
        /// Begin a prime number exploration.
        /// If there is some exploration in progress unsubscribe.
        /// </summary>
        public void IsPrime(int numberToTest)
        {
            if (currentSubscription != null) currentSubscription.Dispose();
            currentSubscription = PrimeNumberIterator(numberToTest)
                                        .ToObservable()
                                        .Subscribe(primeSubject.OnNext);
        }

        /// <summary>
        /// Cancel a prime number exploration
        /// </summary>
        public void Cancel()
        {
            if (currentSubscription != null) currentSubscription.Dispose();
        }
    }

    internal class Program
    {


        private static void Main(string[] args)
        {
            var primeNumberCalculator = new PrimeNumberCalculator();
            primeNumberCalculator.Primes.Subscribe(p => Console.WriteLine("Is prime {0}", p));

            var exit = false;
            do
            {
                Console.WriteLine("Write a number to explore and press enter: ");
                var input = Console.ReadLine();
                int primeToExplore;
                if(int.TryParse(input, out primeToExplore))
                {
                    primeNumberCalculator.IsPrime(primeToExplore);
                }
                else {
                    primeNumberCalculator.Cancel();
                    exit = true;
                }
            } while (!exit);
        }
    }
}

Answer 1

Aquí hay un acercamiento, con el estado mutable:

int lastPrime = 0; // or starting prime
IObservable<int> Primes = 
                Observable.Defer(() =>
{
    do
    {
        lastPrime++;
    } while (!IsPrime(lastPrime));
    return Observable.Return(lastPrime);
}).Repeat();



var disp = Primes.Where(p => p < 1000000).Subscribe(Console.WriteLine);
///    ...
disp.Dispose();