Lesson 5: Creating MoviePlayCounterActor.
As in the previous lesson, we will need to do some preparatory work. First of all, we need to create PlaybackStatisticsActor() the goal of this class is to create a child class MoviePlayCounterActor() and save a link to it.
public class PlaybackStatisticsActor : IActor
{
private PID _moviePlayCounterActorRef;
public Task ReceiveAsync(IContext context)
{
switch (context.Message)
{
case Started msg:
var props = Props.FromProducer(() => new MoviePlayCounterActor());
_moviePlayCounterActorRef = context.Spawn(props);
break;
}
return Task.CompletedTask;
}
}
Next, we need to add a new message IncrementPlayCountMessage() which is used to notify the `MoviePlayCounterActor () ' actor about which movie was started.
public class IncrementPlayCountMessage
{
public string MovieTitle { get; }
public IncrementPlayCountMessage(string movieTitle)
{
MovieTitle = movieTitle;
}
}
Now we need to edit the “Stopped” behavior of the `UserActor () ‘actor so that it sends the message’ IncrementPlayCountMessage ()’ to ‘MoviePlayCounterActor ()’ immediately after starting the movie.
private Task Stopped(IContext context)
{
switch (context.Message)
{
case PlayMovieMessage msg:
_currentlyWatching = msg.MovieTitle;
ColorConsole.WriteLineYellow($"User is currently watching '{_currentlyWatching}'");
context.Send(_moviePlayCounterActorRef, new IncrementPlayCountMessage(_currentlyWatching));
_behavior.Become(Playing);
break;
case StopMovieMessage msg:
ColorConsole.WriteLineRed("Error: cannot stop if nothing is playing");
break;
default:
ColorConsole.WriteLineCyan("UserActor has now become Stopped");
break;
}
return Task.CompletedTask;
}
After this preparatory work, we can finally begin developing the actor MoviePlayCounterActor().
To do this, add a new MoviePlayCounterActor () class to the Actors folder.
public class MoviePlayCounterActor : IActor
{
private Dictionary<string, int> _moviePlayCounts = new Dictionary<string, int>();
public Task ReceiveAsync(IContext context)
{
switch (context.Message)
{
case IncrementPlayCountMessage msg:
ProcessIncrementPlayCountMessage(msg);
break;
}
return Task.CompletedTask;
}
private void ProcessIncrementPlayCountMessage(IncrementPlayCountMessage message)
{
if (!_moviePlayCounts.ContainsKey(message.MovieTitle))
{
_moviePlayCounts.Add(message.MovieTitle, 0);
}
_moviePlayCounts[message.MovieTitle]++;
ColorConsole.WriteMagenta($"MoviePlayerCounterActor '{message.MovieTitle}' has been watched {_moviePlayCounts[message.MovieTitle]} times");
}
}
As you can see, the logic of this actor is straightforward. After receiving the IncrementPlayCountMessage() message, the corresponding movie is searched in _moviePlayCounts dictionary, and if there is one, the counter of this movie is increased by one.
Let’s run our application and look at the result.
