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Do I need to import members of a singleton object into its companion class in Scala?

开发者 https://www.devze.com 2023-01-12 02:57 出处:网络
The Good Book states that: A class and its companion object can access each other’s private members.

The Good Book states that:

A class and its companion object can access each other’s private members.

Perhaps naively, I took this as meaning that a class didn't need to explicitly import t开发者_StackOverflow社区he members from its companion object. I.e., the following would work:

object Foo {
  def bar = 4
 }

class Foo {
 def foo = bar
}

Well, the reason you're reading this is that it doesn't. So do I really need to declare something like this:

class Foo {
  import Foo._

  def foo = bar
}


Yes, you do, just as you state. There's access, and there's scope -- what companion class/objects have is access, not scope.

It's like declaring something public vs private -- it doesn't bring those members into everyone's scope, just give them access to it.


"Can access private members" means that the following works:

object Foo {
  private def bar = 4
}

class Foo {
  def foo = Foo.bar
}


Yes (and I want my 15 points for that!)

But to expand, their scopes do not overlap, so the import is necessary.

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