Rx 可能会让你的生活更轻松。我还想象它会减少代码中的一些潜在竞争条件,并且最终会减少很多管道式代码(即维护缓存的代码)。
如果我首先采用我认为是代码的关键元素(来自https://github.com/schjan/RailNet/blob/master/src/RailNet.Clients.Ecos/Basic/NachrichtenDispo.cs)并拉他们出入我看到的方法。
private bool HasBeginAndEnd(string[] message)
{
bool isValid = true;
if (!message[0].StartsWith("<") || !message[0].EndsWith(">"))
isValid = false;
if (!message.Last().StartsWith("<END"))
isValid = false;
return isValid;
}
private bool IsReplyMessage(string[] message)
{
return message.Length>0 && message[0].StartsWith("<REPLY ");
}
private BasicAntwort ParseResponse(string[] message)
{
string header = message[0].Substring(7, message[0].Length - 8);
return new BasicAntwort(message, header);
}
使用这些漂亮的小描述方法,我可以使用 Rx 创建一个可观察的响应序列。
var incomingMessages = Observable.FromEventPattern<MessageReceivedEventArgs>(
h => _networkClient.MessageReceivedEvent += h,
h => _networkClient.MessageReceivedEvent -= h)
.Select(x => x.EventArgs.Content)
.Where(HasBeginAndEnd)
.Where(IsReplyMessage)
.Select(ParseResponse);
酷,现在我们有一个传入的流/序列。
接下来,我们希望能够发出命令并为其返回适当的响应。Rx 也可以做到这一点。
incomingMessages.Where(reply=>reply.Header == befehl)
为了继续,我们还想添加一个超时,这样如果我们在给定的时间(8000 毫秒?)内没有从 out 命令得到响应,我们应该抛出。我们可以将其转换为任务,如果我们只想要单个值,那么我们也可以使用 Rx 来完成。
incomingMessages.Where(reply=>reply.Header == befehl)
.Timeout(TimeSpan.FromSeconds(2))
.Take(1)
.ToTask();
现在差不多完成了。我们只想要一种发送命令并返回带有响应(或超时)的任务的方法。没问题。只需首先订阅我们传入的消息序列,以避免竞争条件,然后发出命令。
public Task<BasicAntwort> SendCommand(NetworkClient networkClient, string befehl)
{
//Subscribe first to avoid race condition.
var result = incomingMessages
.Where(reply=>reply.Header == befehl)
.Timeout(TimeSpan.FromSeconds(2))
.Take(1)
.ToTask();
//Send command
networkClient.SendMessage(befehl);
return result;
}
这是作为 LinqPad 脚本的整个代码
void Main()
{
var _networkClient = new NetworkClient();
var sendCommandTask = SendCommand(_networkClient, "MyCommand");
BasicAntwort reply = sendCommandTask.Result;
reply.Dump();
}
private static bool HasBeginAndEnd(string[] message)
{
bool isValid = true;
if (!message[0].StartsWith("<") || !message[0].EndsWith(">"))
isValid = false;
if (!message.Last().StartsWith("<END"))
isValid = false;
return isValid;
}
private static bool IsReplyMessage(string[] message)
{
return message.Length>0 && message[0].StartsWith("<REPLY ");
}
private static BasicAntwort ParseResponse(string[] message)
{
string header = message[0].Substring(7, message[0].Length - 8);
return new BasicAntwort(message, header);
}
public IObservable<BasicAntwort> Responses(NetworkClient networkClient)
{
return Observable.FromEventPattern<MessageReceivedEventArgs>(
h => networkClient.MessageReceivedEvent += h,
h => networkClient.MessageReceivedEvent -= h)
.Select(x => x.EventArgs.Content)
.Where(HasBeginAndEnd)
.Where(IsReplyMessage)
.Select(ParseResponse);
}
public Task<BasicAntwort> SendCommand(NetworkClient networkClient, string befehl)
{
//Subscribe first to avoid race condition.
var result = Responses(networkClient)
.Where(reply=>reply.Header == befehl)
.Timeout(TimeSpan.FromSeconds(2))
.Take(1)
.ToTask();
//Send command
networkClient.SendMessage(befehl);
return result;
}
public class NetworkClient
{
public event EventHandler<MessageReceivedEventArgs> MessageReceivedEvent;
public bool Connected { get; set; }
public void SendMessage(string befehl)
{
var handle = MessageReceivedEvent;
if(handle!=null){
var message = new string[3]{"<REPLY " + befehl +">", "Some content", "<END>"};
handle(this, new UserQuery.MessageReceivedEventArgs(){Content=message});
}
}
}
public class MessageReceivedEventArgs : EventArgs
{
public string[] Content { get; set; }
}
public class BasicAntwort
{
public BasicAntwort(string[] message, string header)
{
Header = header;
Message = message;
}
public string Header { get; set; }
public string[] Message { get; set; }
}