匹配Java接口時的Scala匹配/ case語句

Question

我正在使用Scala match/case語句來匹配給定java類的接口。我希望能夠檢查一個類是否實現了接口的組合。我似乎得到這個工作的唯一方法是使用嵌套的match/case陳述，這看起來很醜。

可以說我有一個PersonImpl對象，它實現了Person，Manager和Investor。我想看看PersonImpl是否實現了經理和投資者。我應該可以做到以下幾點：

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。爲了得到它的工作，我必須做到以下看起來很醜陋。

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. 
} 

這簡直太難看了。有什麼建議麼？

Answer 1

試試這個：

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

with用於其它情況下，您可能想表達型路口，例如在類型限制：

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

順便說一句 - 不，這是建議的做法，但是 - 你隨時可以測試它像這樣還有：if (person.isInstanceOf[Manager] && person.isInstanceOf[Investor]) ...。

---

編輯：這很適合我：

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 
}