/// <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();
});
}
/// <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 <T> > ToAsync <T>(this 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();
});
}
static AsyncSubject<T> Cancel<T>(AsyncSubject<T> subject, CancellationToken cancellationToken)
{
subject.OnError(new OperationCanceledException(cancellationToken));
return subject;
}
