如何在 Ruby 中创建私有类常量

发布于 2024-09-02 09:38:01 字数 252 浏览 6 评论 0原文

在 Ruby 中如何创建私有类常量？（即在班级内部可见但外部不可见）

class Person
  SECRET='xxx' # How to make class private??

  def show_secret
    puts "Secret: #{SECRET}"
  end
end

Person.new.show_secret
puts Person::SECRET # I'd like this to fail

原文

In Ruby how does one create a private class constant?
(i.e one that is visible inside the class but not outside)

class Person
  SECRET='xxx' # How to make class private??

  def show_secret
    puts "Secret: #{SECRET}"
  end
end

Person.new.show_secret
puts Person::SECRET # I'd like this to fail

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暗恋未遂 2024-09-09 09:38:01

从 ruby 1.9.3 开始，您拥有 Module#private_constant 方法，这似乎正是您想要的：

class Person
  SECRET='xxx'.freeze
  private_constant :SECRET

  def show_secret
    puts "Secret: #{SECRET}"
  end
end

Person.new.show_secret
# => "Secret: xxx"

puts Person::SECRET
# NameError: private constant Person::SECRET referenced

Starting on ruby 1.9.3, you have the Module#private_constant method, which seems to be exactly what you wanted:

class Person
  SECRET='xxx'.freeze
  private_constant :SECRET

  def show_secret
    puts "Secret: #{SECRET}"
  end
end

Person.new.show_secret
# => "Secret: xxx"

puts Person::SECRET
# NameError: private constant Person::SECRET referenced

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稚气少女 2024-09-09 09:38:01

您还可以将常量更改为类方法：

def self.secret
  'xxx'
end

private_class_method :secret

这使得它可以在类的所有实例中访问，但不能在外部访问。

You can also change your constant into a class method:

def self.secret
  'xxx'
end

private_class_method :secret

This makes it accessible within all instances of the class, but not outside.

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伪心 2024-09-09 09:38:01

您可以使用 @@class_variable 代替常量，它始终是私有的。

class Person
  @@secret='xxx' # How to make class private??

  def show_secret
    puts "Secret: #{@@secret}"
  end
end
Person.new.show_secret
puts Person::@@secret
# doesn't work
puts Person.class_variable_get(:@@secret)
# This does work, but there's always a way to circumvent privateness in ruby

当然，然后 ruby 不会采取任何措施来强制 @@secret 的恒定性，但是 ruby 几乎不会采取任何措施来强制强制恒定性，所以......

Instead of a constant you can use a @@class_variable, which is always private.

class Person
  @@secret='xxx' # How to make class private??

  def show_secret
    puts "Secret: #{@@secret}"
  end
end
Person.new.show_secret
puts Person::@@secret
# doesn't work
puts Person.class_variable_get(:@@secret)
# This does work, but there's always a way to circumvent privateness in ruby

Of course then ruby will do nothing to enforce the constantness of @@secret, but ruby does very little to enforce constantness to begin with, so...

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呆橘 2024-09-09 09:38:01

嗯...

@@secret = 'xxx'.freeze

有点作品。

Well...

@@secret = 'xxx'.freeze

kind of works.

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与风相奔跑 2024-09-09 09:38:01

您可以首先将其设为私有方法

You can just literally make it a private method in the first place ????????‍♂️

class Person
  def SECRET
    'xxx'
  end

  def show_secret
    puts SECRET
  end
end

Person::SECRET    # Error: No such constant
Person.SECRET     # Error: No such method
Person.new.SECRET # Error: Call private method
person.new.show_secret # prints "xxx"

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~没有更多了~