Ruby中的私有模块方法

我认为实现这一点的最佳方法(主要是现有lib的编写方式)是在模块内创建一个处理所有逻辑的类,而模块只是提供了一个方便的方法,例如。

module GTranslate
  class Translator
    def perform( text ); translate( text ); end

    private

    def translate( text )
      # do some private stuff here
    end
  end

  def self.translate( text )
    t = Translator.new
    t.perform( text )
  end
end

还有 Module.private_class_method

module Foo
  def self.included(base)
    base.instance_eval do
      def method_name
        # ...
      end
      private_class_method :method_name
    end
  end
end

关于问题中的代码:

module Thing
  def self.pub; puts "Public method"; end
  def self.priv; puts "Private method"; end
  private_class_method :priv
end

Ruby 2.1或更新版本:

module Thing
  def self.pub; puts "Public method"; end
  private_class_method def self.priv; puts "Private method"; end
end

module Writer
  class << self
    def output(s)
      puts upcase(s)
    end

    private

    def upcase(s)
      s.upcase
    end
  end
end

Writer.output "Hello World"
# -> HELLO WORLD

Writer.upcase "Hello World"
# -> so.rb:16:in `<main>': private method `upcase' called for Writer:Module (NoMethodError)

module Foo
  def self.included(base)
    class << base 
      def public_method
        puts "public method"
      end
      def call_private
        private_method
      end
      private
      def private_method
        puts "private"
      end
    end
  end
end

class Bar
  include Foo
end

Bar.public_method

begin
  Bar.private_method
rescue
  puts "couldn't call private method"
end

Bar.call_private

不幸地 private 仅适用于实例方法。在类中获取私有“静态”方法的一般方法是执行以下操作:

class << self
  private

  def foo()
   ....
  end
end

诚然,我没有在模块中玩过这个。

一个好方法就是这样

module MyModule
  class << self
    def public_method
      # you may call the private method here
      tmp = private_method
      :public
    end

    private def private_method
      :private
    end
  end
end

# calling from outside the module
puts MyModule::public_method

module Thing
  extend self

  def pub
    puts priv(123)
  end

  private
  
  def priv(value)
    puts "Private method with value #{value}"
  end
end

Thing.pub
# "Private method with value 123"

Thing.priv
# NoMethodError (private method `priv' called for Thing:Module)

在类变量/常量中将方法存储为lambda有什么意义?

module MyModule
  @@my_secret_method = lambda {
    # ...
  }
  # ...
end

对于测试:
UPD:这段代码在6年后进行了巨大的更新 d

module A
  @@L = lambda{ "@@L" }
  def self.a ; @@L[] ; end
  def self.b ; a ; end

  class << self
    def c ; @@L[] ; end
    private
    def d ; @@L[] ; end
  end
  def self.e ; c ; end
  def self.f ; self.c ; end
  def self.g ; d ; end
  def self.h ; self.d ; end

  private
  def self.i ; @@L[] ; end
  class << self
    def j ; @@L[] ; end
  end

  public
  def self.k ; i ; end
  def self.l ; self.i ; end
  def self.m ; j ; end
  def self.n ; self.j ; end
end

for expr in %w{ A.a A.b A.c A.d A.e A.f A.g A.h A.i A.j A.k A.l A.m A.n }
  puts "#{expr} => #{begin ; eval expr ; rescue => e ; e ; end}"
end

在这里我们看到:

A.a => @@L
A.b => @@L
A.c => @@L
A.d => private method `d' called for A:Module
A.e => @@L
A.f => @@L
A.g => @@L
A.h => private method `d' called for A:Module
A.i => @@L
A.j => @@L
A.k => @@L
A.l => @@L
A.m => @@L
A.n => @@L

1) @@L 无法从外部访问,但几乎可以从任何地方访问
class << self ; private ; def 成功地实现了该方法 D 从外部和内部无法使用 self.
3) private ; self. 和 private ; class << self 不要将方法设置为私有的——它们在有和无条件下都是可访问的 自己

创建专用模块或类

常数永远不是私有的。但是,可以创建模块或类,而无需将其分配给常量。

因此,这是一个替代方案 :private_class_method

module PublicModule
  def self.do_stuff(input)
    @private_implementation.do_stuff(input)
  end

  @private_implementation = Module.new do
    def self.do_stuff(input)
      input.upcase # or call other methods on module
    end
  end
end

用法:

PublicModule.do_stuff("whatever") # => "WHATEVER"

Module.new 和 Class.new .

下面是一个解决方案,通过使用 extend

module SomeModule

  class ClassThatDoesNotExtendTheModule
    class << self
      def random_class_method
        private_class_on_module
      end
    end
  end

  class ClassThatDoesExtendTheModule
    extend SomeModule
  
    class << self
      def random_class_method
        private_class_on_module
      end
    end
  end

  class AnotherClassThatDoesExtendTheModule
    extend SomeModule
  
    class << self
      def random_class_method
        private_class_on_module
      end
    end
  end

  private

  def private_class_on_module
    puts 'some private class was called'
  end
  
end

> SomeModule::ClassThatDoesNotExtendTheModule.random_class_method

NameError: undefined local variable or method `private_class_on_module' for SomeModule::ClassThatDoesNotExtendTheModule:Class


> SomeModule::ClassThatDoesExtendTheModule.random_class_method

some private class was called


> SomeModule::ClassThatDoesExtendTheModule.private_class_on_module

NoMethodError: private method `private_class_on_module' called for SomeModule::ClassThatDoesExtendTheModule:Class


> SomeModule::AnotherClassThatDoesExtendTheModule.random_class_method

some private class was called


> SomeModule::AnotherClassThatDoesExtendTheModule.random_class_method

NoMethodError: private method `private_class_on_module' called for SomeModule::AnotherClassThatDoesExtendTheModule:Class