Scala:抽象类型模式A未被选中，因为通过擦除将其消除 [英] Scala: abstract type pattern A is unchecked since it is eliminated by erasure

问题描述

我正在编写仅可捕获特定类型异常的函数.

I am writing the function that can catch exceptions of the certain type only.

def myFunc[A <: Exception]() {
    try {
        println("Hello world") // or something else
    } catch {
        case a: A => // warning: abstract type pattern A is unchecked since it is eliminated by erasure
    }
}

在这种情况下绕过jvm类型擦除的正确方法是什么?

What is the corrent way to bypass jvm type erasure in such case?

推荐答案

您可以像中那样使用 ClassTag 这个答案.

You could use ClassTag like in this answer.

但是我更喜欢这种方法:

But I'd prefer this approach:

def myFunc(recover: PartialFunction[Throwable, Unit]): Unit = {
  try {
    println("Hello world") // or something else
  } catch {
    recover
  }
}

用法:

myFunc{ case _: MyException => }

使用 ClassTag :

import scala.reflect.{ClassTag, classTag}

def myFunc[A <: Exception: ClassTag](): Unit = {
  try {
    println("Hello world") // or something else
  } catch {
    case a if classTag[A].runtimeClass.isInstance(a) =>
  }
}

还请注意，通常应将 Try 与 recover 方法一起使用: Try 将仅捕获

Note also that in general you should use Try with recover method: Try will catch only NonFatal exceptions.

def myFunc(recover: PartialFunction[Throwable, Unit]) = {
  Try {
    println("Hello world") // or something else
  } recover {
    recover
  }.get // you could drop .get here to return `Try[Unit]`
}

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