为什么我的对象不是包<root>的成员如果它在一个单独的源文件中? [英] Why is my object not a member of package <root> if it's in a separate source file?

问题描述

我在访问根包中定义的对象时遇到问题.如果我将所有代码都放在一个文件中，它可以正常工作，但是当我将它分成两个文件时，我无法通过编译器.

I'm having a problem accessing an object defined in the root package. If I have all my code in one file, it works fine, but when I split it across two files, I can't get it past the compiler.

这很好用:

全部在一个名为 packages.scala 的文件中:

All in one file called packages.scala:

object Foo
  val name = "Brian"
}

package somepackage {
  object Test extends App {
    println(Foo.name)
  }
}

证人:

$ scalac packages.scala
$ scala -cp . somepackage.Test
Brian

但如果我将代码拆分为两个文件:

But if I split the code across two files:

packages.scala

object Foo {
  val name = "Brian"
}

packages2.scala

package somepackage {
  object Test extends App {
    println(Foo.name)
  }
}

一切都失败了:

$ scalac packages.scala packages2.scala
packages2.scala:3: error: not found: value Foo

所以我尝试将 Foo 的引用设为绝对:

So I try to make the reference to Foo absolute:

...
    println(_root_.Foo.name)
...

但这也不起作用:

$ scalac packages.scala packages2.scala
packages2.scala:3: error: object Foo is not a member of package <root>

如果 Foo 不是根包的成员，那么它到底在哪里 ?

If Foo is not a member of the root package, where on earth is it?

推荐答案

我认为这是规范中的相关部分:

I think this is the relevant part in the spec:

包装之外的顶级定义被假定注入到一个特殊的空包中.该包无法命名，因此无法导入.但是，空包的成员彼此可见，无需限定.

Top-level definitions outside a packaging are assumed to be injected into a special empty package. That package cannot be named and therefore cannot be imported. However, members of the empty package are visible to each other without qualification.

来源Scala 参考§9.2 包.

但是如果你在 packages2.scala 中有以下内容，不要问我为什么它有效:

But don’t ask me why it works if you have the following in packages2.scala:

object Dummy

package somepackage {
  object Test extends App {
    println(Foo.name)
  }
}

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