ruby - 从 Ruby 中的模块函数访问私有(private)方法

Question

我正在尝试为模块函数创建私有(private)辅助方法，但无济于事。我觉得我缺少一些非常简单的东西。

更新的示例具有更易于理解的用例:

module FancyScorer
  module_function

  def score(ary)
    scores = []
    ary.each_slice(2).with_index do |slice, i|
      scores <<
        case i % 2
        when 0
          score_eventh(ary)
        else
          score_oddth(ary)
        end
    end
    scores.inject(:+)
  end

  private

  def score_eventh(ary)
    ary.inject(:+) / (ary.size - 1)
  end

  def score_oddth(ary)
    ary.inject(:*) / (ary.size - 1)
  end
end

FancyScorer.score([1,2,3,4])
# => `block in score_curiously': undefined method `score_eventh'
#    for FancyScorer:Module (NoMethodError)

注意:私有(private)方法应保持私有(private)。

这是用例:有几个模块包含各种评分技术，例如FancyScorer、SimpleScorer、ComplexScorer。这些函数是独立测试的，然后被用来为不同的类创建一个score方法。例如:

class A
  ...
  def score    
    FancyScorer.score(metrics) + 2*SimpleScorer.score(metrics)
  end
end

class B
  ...
  def score
    0.5*FancyScorer.score(metrics) + 2*SimpleScorer.score(metrics[0,3]) + ComplexScorer.score(metrics)
  end
end

没有提供用例的先前示例:

module Party
  module_function

  def pooper
    enjoy
  end

  private

  def enjoy
    puts "Wahoo!"
  end
end

Party.pooper
# => NameError: undefined local variable or method `enjoy' for Party:module
#            from (party): in `pooper`

Answer 1

module_function(symbol, ...) → self说:-

Creates module functions for the named methods. These functions may be called with the module as a receiver, and also become available as instance methods to classes that mix in the module. Module functions are copies of the original, and so may be changed independently. The instance-method versions are made private. If used with no arguments, subsequently defined methods become module functions.

您需要确保将辅助方法声明为 #private_class_method:private 仅影响实例方法。

module Party

  def enjoy
    puts 'hello'
  end

  def pooper
    enjoy
  end

  private_class_method :enjoy
  module_function :pooper
end

Party.pooper # => 'hello'
Party.enjoy # => private method `enjoy' called for Party:Module (NoMethodError)

此外，您应该注意可访问性关键字的顺序，例如 public、private 和 module_function。 这些不重叠，而是覆盖。

module Party
  module_function # Module function declarations begin
  def pooper
    bar
  end
  def bar
    enjoy
  end

  private         # Private declarations begin, module function declarations end
  module_function # Private declarations end, module function declarations begin
  def enjoy       # Therefore, this is a module function
    "Wahoo!"
  end
end

Party.pooper # => "Wahoo!"
Party.bar # => "Wahoo!"
Party.enjoy # => "Wahoo!"  <-- No longer private

注意这里 module_function 覆盖了之前的 private 声明。

---

这里有更多示例 module_function 何时会完成其工作，何时不会。

一旦弹出另一个可访问性关键字，module_function 定义就会停止。在此示例中，module_function 被 public 中断，使 #pooper 成为公共(public)实例方法。使用 private 会类似地阻止 module_method。

module Party
  module_function
  public
  def pooper
    "i am pooper"
  end
end

Party.pooper
# undefined method `pooper' for Party:Module (NoMethodError)

现在如果顺序改变了:

module Party
  public
  module_function
  def pooper
    "i am pooper"
  end
end

Party.pooper # => "i am pooper"