访问修饰符的Scala参数？ [英] Scala parameters for access modifiers?

问题描述

What is the difference between

class Test {
  private[this] val foo = 0
}

vs

class Test {
  private val foo = 0
}

[] 里面有什么？另外，当我要查找此规格时应该搜索什么？我尝试了谷歌搜索 scala访问修饰符参数/参数化的scala访问修饰符的各种组合，但没有结果。

What all can go inside the []? Also, what should I search for when I want to look up the specs of this? I tried Googling various combinations of "scala access modifier arguments/parametrized scala access modifier" and nothing came up.

推荐答案

当我要查找此规格时应该搜索什么？

what should I search for when I want to look up the specs of this?

在 Scala语言规范，它被定义为访问修饰符和访问限定符（请参见BNF §5.2）。

In The Scala Language Specification it is defined as "access modifier" and "access qualifier" (see BNF in §5.2).

What is the difference between

...有什么区别/ p>

...

所有内容都可以放入[]？

What all can go inside the []?

您可以在此处放置类名称，包名称或此 。以下是语言规范中的相关引文对此进行了解释（有关更多详细信息，请参见§5.2）：

You can put class name, package name or this there. Here is a relevant quote from language specs that explains this (see §5.2 for more details):

修饰符可以用标识符限定必须
表示包围该定义的类或包的C（例如private [C]）。带有
这样修饰符的成员只能分别从
C包中的代码或仅从C类及其配套模块（第5.4节）中的代码访问。

The modifier can be qualified with an identifier C (e.g. private[C ]) that must denote a class or package enclosing the definition. Members labeled with such a modifier are accessible respectively only from code inside the package C or only from code inside the class C and its companion module (§5.4).

另一种形式的资格是私人[this]。用该修饰符标记为
的成员M称为对象保护的；只能从定义它的对象内的
访问它。也就是说，对于前缀为O的某些类，仅当前缀为this或O.this时，选择p.M才是合法的。除
外，还适用不合格的私人限制。

An different form of qualification is private[this]. A member M marked with this modifier is called object-protected; it can be accessed only from within the object in which it is defined. That is, a selection p.M is only legal if the prefix is this or O.this, for some class O enclosing the reference. In addition, the restrictions for unqualified private apply.

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