public static Func <T1, T2, IObservable <TResult> > FromAsyncPattern <T1, T2, TResult>(Func <T1, T2, AsyncCallback, object, IAsyncResult> begin, Func <IAsyncResult, TResult> end)
{
return((x, y) =>
{
var subject = new AsyncSubject <TResult>();
try
{
begin(x, y, iar =>
{
TResult result;
try
{
result = end(iar);
}
catch (Exception exception)
{
subject.OnError(exception);
return;
}
subject.OnNext(result);
subject.OnCompleted();
}, null);
}
catch (Exception exception)
{
return Observable.Throw <TResult>(exception, Scheduler.DefaultSchedulers.AsyncConversions);
}
return subject.AsObservable();
});
}
public static Func <IObservable <T> > ToAsync <T>(Func <T> function, IScheduler scheduler)
{
return(() =>
{
var subject = new AsyncSubject <T>();
scheduler.Schedule(() =>
{
var result = default(T);
try
{
result = function();
}
catch (Exception exception)
{
subject.OnError(exception);
return;
}
subject.OnNext(result);
subject.OnCompleted();
});
return subject.AsObservable();
});
}
private static IObservable <TResult> ToObservableResult <TResult>(AsyncSubject <TResult> subject, IScheduler scheduler)
{
if (scheduler != null)
{
return(subject.ObserveOn(scheduler));
}
else
{
return(subject.AsObservable());
}
}
/// <summary>
/// <para>Create an Observable that emits the return value of a function-like directive asynchronously</para>
///
/// <para>There are a number of ways that programming languages have for obtaining values as
/// the result of calculations, with names like functions, futures, actions, callables,
/// runnables, and so forth. The operators grouped here under the Start operator category
/// make these things behave like Observables so that they can be chained with other
/// Observables in an Observable cascade</para>
/// </summary>
/// <see cref="http://reactivex.io/documentation/operators/start.html"/>
public static Func <IObservable <Unit> > ToAsync(this Action action, IScheduler scheduler)
{
return(() => {
var subject = new AsyncSubject <Unit>();
scheduler.Schedule(() => {
try {
action();
} catch (Exception exception) {
subject.OnError(exception);
return;
}
subject.OnNext(Unit.Default);
subject.OnCompleted();
});
return subject.AsObservable();
});
}
