为什么我不能创建一个泛型类型的数组？

This does not work:

这不起作用：

def giveArray[T](elem:T):Array[T] = {
    new Array[T](1)
  }

But this does:

但这样做：

  def giveList[T](elem:T):List[T] = {
    List.empty[T]
  }

I am sure this is a pretty basic thing and I know that Arrays can behave a bit unusual in Scala.

我确信这是一个非常基本的东西，我知道Arrays在Scala中的行为有点不寻常。

Could someone explain to me how to create such an Array and also why it doesn't work in the first place?

有人可以向我解释如何创建这样一个数组，以及为什么它不起作用？

1 个解决方案

#1

This is due to JVM type erasure. Manifest were introduce to handle this, they cause type information to be attached to the type T. This will compile:

这是由于JVM类型擦除。引入Manifest来处理这个问题，它们会将类型信息附加到类型T上。这将编译：

def giveArray[T: Manifest](elem:T):Array[T] = {
  new Array[T](1)
}

There are nearly duplicated questions on this. Let me see if I can dig up. See http://www.scala-lang.org/docu/files/collections-api/collections_38.html for more details. I quote (replace evenElems with elem in your case)

对此有几乎重复的问题。让我看看我是否可以挖掘。有关详细信息，请参阅http://www.scala-lang.org/docu/files/collections-api/collections_38.html。我引用（在你的情况下用elem替换evenElems）

What's required here is that you help the compiler out by providing some runtime hint what the actual type parameter of evenElems is

这里需要的是通过提供一些运行时提示来帮助编译器，提示evenElems的实际类型参数是什么

In particular you can also use ClassManifest.

特别是你也可以使用ClassManifest。

def giveArray[T: ClassManifest](elem:T):Array[T] = {
  new Array[T](1)
}

#1