private async Task Continue()
{
Fetching = true;
// At the time of writing the sample service provided by reqres.in
// exposes 12 users with id's in [1..12]
int userId = _randomizer.Next() % 12 + 1;
// https://stackoverflow.com/a/5838632/12207453
BuddyAvatarBitmap?.Dispose();
BuddyAvatarBitmap = null;
// https://rehansaeed.com/reactive-extensions-rx-part-8-timeouts/
using (var timeoutTokenSource = new CancellationTokenSource(_fetchTimeoutSpan)) {
var userDtoFetcherTask =
"https://reqres.in/api/"
.AppendPathSegments("users", userId)
.GetJsonAsync <UserDto>(timeoutTokenSource.Token);
try {
var user = await userDtoFetcherTask;
_userAvatarUrl = user.Data.AvatarUrl;
BuddyName = $"{user.Data.FirstName} {user.Data.LastName}";
}
catch {
Console.WriteLine("Could not fetch buddy info");
}
}
Fetching = false;
// https://rehansaeed.com/reactive-extensions-part1-replacing-events/
_triggeringTheTimer.OnNext(TimerTrigger.Start);
}
public MainViewModel()
{
Activator = new ViewModelActivator();
IsTimerRunning = false;
this.WhenActivated(
disposables => {
Disposable
// https://stackoverflow.com/a/5838632/12207453
.Create(() => BuddyAvatarBitmap?.Dispose())
.DisposeWith(disposables);
});
var canInitiateNewFetch =
this.WhenAnyValue(vm => vm.Fetching, fetching => !fetching);
// https://reactiveui.net/docs/handbook/commands/
// https://reactiveui.net/docs/handbook/scheduling/
// https://blog.jonstodle.com/task-toobservable-observable-fromasync-task/
// https://github.com/reactiveui/ReactiveUI/issues/1245
StalkCommand =
ReactiveCommand.CreateFromObservable(
() => Observable.StartAsync(Stalk),
canInitiateNewFetch,
RxApp.MainThreadScheduler
);
ContinueCommand =
ReactiveCommand.CreateFromObservable(
() => Observable.StartAsync(Continue),
canInitiateNewFetch,
RxApp.MainThreadScheduler
);
// Run the "Continue" command once in the beginning in order to fetch the first buddy.
// https://reactiveui.net/docs/handbook/when-activated/#no-need
ContinueCommand.Execute().Subscribe();
// https://reactiveui.net/docs/handbook/commands/canceling#canceling-via-another-observable
var startTimerCommand = ReactiveCommand.CreateFromObservable(
() =>
Observable
.Return(Unit.Default)
.Delay(TimeSpan.FromMilliseconds(DecisionTimeMilliseconds))
.TakeUntil(
TriggeringTheTimer
.Where(trigger => trigger == TimerTrigger.Stop)));
startTimerCommand.Subscribe(_ => ContinueCommand.Execute().Subscribe());
this
.WhenAnyObservable(vm => vm.TriggeringTheTimer)
.Do(trigger => {
if (trigger == TimerTrigger.Start)
{
startTimerCommand.Execute().Subscribe();
IsTimerRunning = true;
}
else
{
IsTimerRunning = false;
}
})
.Subscribe();
}
