匹配Java接口时的Scala匹配/ case语句

Question

我正在使用Scala match/case语句来匹配给定java类的接口。我希望能够检查一个类是否实现了接口的组合。我似乎得到这个工作的唯一方法是使用嵌套的match/case陈述，这看起来很丑。

可以说我有一个PersonImpl对象，它实现了Person，Manager和Investor。我想看看PersonImpl是否实现了经理和投资者。我应该可以做到以下几点：

person match { 
    case person: (Manager, Investor) => 
    // do something, the person is both a manager and an investor 
    case person: Manager => 
    // do something, the person is only a manager 
    case person: Investor => 
    // do something, the person is only an investor 
    case _ => 
    // person is neither, error out. 
} 

case person: (Manager, Investor)只是不起作用。为了得到它的工作，我必须做到以下看起来很丑陋。

person match { 
    case person: Manager = { 
    person match { 
     case person: Investor => 
     // do something, the person is both a manager and investor 
     case _ => 
     // do something, the person is only a manager 
    } 
    case person: Investor => 
    // do something, the person is only an investor. 
    case _ => 
    // person is neither, error out. 
} 

这简直太难看了。有什么建议么？

Answer 1

试试这个：

case person: Manager with Investor => // ... 

with用于其它情况下，您可能想表达型路口，例如在类型限制：

def processGenericManagerInvestor[T <: Manager with Investor](person: T): T = // ... 

顺便说一句 - 不，这是建议的做法，但是 - 你随时可以测试它像这样还有：if (person.isInstanceOf[Manager] && person.isInstanceOf[Investor]) ...。

---

编辑：这很适合我：

trait A 
trait B 
class C 

def printInfo(a: Any) = println(a match { 
    case _: A with B => "A with B" 
    case _: A => "A" 
    case _: B => "B" 
    case _ => "unknown" 
}) 

def main(args: Array[String]) { 
    printInfo(new C)    // prints unknown 
    printInfo(new C with A)  // prints A 
    printInfo(new C with B)  // prints B 
    printInfo(new C with A with B) // prints A with B 
    printInfo(new C with B with A) // prints A with B 
}