模块如何解析常量的作用域? [英] How Do Modules Resolve A Constant's Scope?

问题描述

我一直在阅读这本Ruby书，然后有一个我不太了解的示例:

I've been reading this Ruby book, then there's this example that I haven't well understood :

CONST = "outer"
module Mod
    CONST = 1
    def Mod.method1
        # module method
        CONST + 1
    end
end
module Mod::Inner
    def (Mod::Inner).method2
        CONST + " scope"
    end
end
Mod::CONST  # => 1
Mod.method1 # => 2
Mod::Inner::method2 # => "outer scope"

请您向我解释一下(详细解释)，以便我可以完全理解该作用域在Ruby中的工作方式. 谢谢.

Would you please explain this to me (a detailed explanation) so I can fully understand how the scope works in Ruby. Thank you.

推荐答案

Ruby的常量(以大写字母开头的标识符)可根据定义/访问它们的 lexical 范围进行访问.

Constants in Ruby (identifiers beginning with a capital letter) are accessible based on the lexical scope in which they are defined/accessed.

在method1中，Mod范围内的CONST优先于最外面的CONST.在method2中，Mod范围内的CONST在词法上不可见，因此可以访问最外面的CONST.

In method1, the CONST within the Mod scope takes precedence over the outermost CONST. In method2, the CONST within the Mod scope is not visible lexically, so the outermost CONST is accessed.

对于方法定义本身，当名称使用前面的模块常量(例如，Mod或Mod::Inner)限定时，该方法被定义为模块方法"，而不是(默认).

As for the method definitions themselves, when the name is qualified with a preceding module constant (e.g. Mod or Mod::Inner), the method is defined as a "module method" rather than as an instance method of self.class (the default).

模块/方法层次结构中的名称用::分隔，或者在模块和模块方法之间用分隔符的情况下，用.分隔.

Names in the module/method hierarchy are separated by :: or, alternatively in the case of the separator between the module and the module method, a ..

更新:请注意，method2常量对method2不可见的原因是Mod没有单独打开".该定义直接跳到Mod::Inner.如果代码更改为:

Update: Note that the reason why Mod's constants are not visible to method2 is that Mod was not separately "opened". The definition skipped directly to Mod::Inner. If the code were changed to:

module Mod
  module Inner
    def (Mod::Inner).method2
      ...

然后Mod的常量将可供method2访问，并优先于外部范围中的任何常量.

Then Mod's constants would be accessible to method2 and take precedence over any in the outer scope.

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