在实践中与Scala actor编写应用程序 [英] Writing applications with Scala actors in practice

问题描述

我现在已经使用Scala actor编写了一些应用程序，并且我对人们如何处理或处理我遇到的一些问题很感兴趣。

I've now written a few applications using scala actors and I'm interested in how people have approached or dealt with some of the problems I've encountered.

过多的消息类或！？

我有一个actor，它对用户操作做出反应，必须引起某些事情发生。假设它对消息 UserRequestsX（id） 反应 s。我一直面临的一个问题是，由于我想对程序进行模块化，因此一个单独的参与者无法在不涉及其他参与者的情况下完成操作。例如，假设我需要使用 id 参数来检索一堆值，然后需要通过其他角色将其删除。如果我正在编写普通的Java程序，则可能会执行以下操作：

I have an actor which reacts to a user operation and must cause something to happen. Let's say it reacts to a message UserRequestsX(id). A continuing problem I have is that, because I want to modularize my programs, a single actor on its own is unable to complete the action without involving other actors. For example, suppose I need to use the id parameter to retrieve a bunch of values and then these need to be deleted via some other actor. If I were writing a normal Java program, I might do something like:

public void reportTrades(Date date) {
    Set<Trade> trades = persistence.lookup(date);
    reportService.report(trades);
}

这很简单。但是，使用演员会有点麻烦，因为我想避免使用 ！？ 。一个参与者对 ReportTrades（date）消息做出反应，但必须向 PersistenceActor 进行交易，然后要求 ReportActor 进行报告。我发现这样做的唯一方法是：

Which is simple enough. However, using actors this becomes a bit of a pain because I want to avoid using !?. One actor reacts to the ReportTrades(date) message but it must ask a PersistenceActor for the trades and then a ReportActor to report them. The only way I've found of doing this is to do:

react {
    case ReportTrades(date) =>
       persistenceActor ! GetTradesAndReport(date)
}

因此在我的 PersistenceActor 我有一个react块：

So that in my PersistenceActor I have a react block:

react {
    case GetTradesAndReport(date) =>
       val ts = trades.get(date) //from persietent store
       reportActor ! ReportTrades(ts)
}

但是现在我有2个问题：

But now I have 2 problems:

1. 我必须创建额外的消息类来表示相同的请求（即报告交易）。实际上，在这种情况下，我有三个，但我可能还有更多-跟踪这些问题变得很困难


2. 我应该如何称呼第一条消息和第三条消息 ReportTrades ？将它们都称为 ReportTrades 会造成混淆（或者，如果我这样做，则必须将它们放在单独的包装中）。基本上，没有这样的事情，例如 val 类型的重载。

1. I have to create extra message classes to represent the same request (i.e. "report trades"). In fact I have three in this scenario but I may have many more - it becomes a problem keeping track of these
2. What should I call the first and third message ReportTrades? It's confusing to call them both ReportTrades (or if I do, I must put them in separate packages). Essentially there is no such thing as overloading a class by val type.

我缺少什么吗？我可以避免吗？我应该放弃并使用 ！？ 吗？人们是否使用某种组织结构来阐明正在发生的事情？

Is there something I'm missing? Can I avoid this? Should I just give up and use !? Do people use some organizational structure to clarify what is going on?

推荐答案

对我来说，您的 ReportTrades 消息正在混合两个不同的概念。一个是请求，顺序是响应。例如，它们可能被命名为 GetTradesReport（Date）和 SendTradesReport（List [Trade]）。或者，也许是 ReportTradesByDate（Date）和 GenerateTradesReport（List [Trade]）。

To me, your ReportTrades message is mixing two different concepts. One is a Request, the order is a Response. They might be named GetTradesReport(Date) and SendTradesReport(List[Trade]), for example. Or, maybe, ReportTradesByDate(Date) and GenerateTradesReport(List[Trade]).

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