有没有一种方法可以从Ruby中的实例调用私有Class方法？ [英] Is there a way to call a private Class method from an instance in Ruby?

问题描述

除了 self.class.send之外：方法，参数... 当然。我想在类和实例级别上提供一个相当复杂的方法，而不必复制代码。

Other than self.class.send :method, args..., of course. I'd like to make a rather complex method available at both the class and instance level without duplicating the code.

更新：

@Jonathan Branam：这是我的假设，但我想确保没有其他人找到解决方法。 Ruby中的可见性与Java中的可见性非常不同。您也很正确， private 不适用于类方法，尽管这会声明一个私有类方法：

@Jonathan Branam: that was my assumption, but I wanted to make sure nobody else had found a way around. Visibility in Ruby is very different from that in Java. You're also quite right that private doesn't work on class methods, though this will declare a private class method:

class Foo
  class <<self
    private
    def bar
      puts 'bar'
    end
  end
end

Foo.bar
# => NoMethodError: private method 'bar' called for Foo:Class

推荐答案

这里是与问题一起出现的代码段。在类定义中使用私有不适用于类方法。您需要使用以下示例中的 private_class_method。

Here is a code snippet to go along with the question. Using "private" in a class definition does not apply to class methods. You need to use "private_class_method" as in the following example.

class Foo
  def self.private_bar
    # Complex logic goes here
    puts "hi"
  end
  private_class_method :private_bar
  class <<self
    private
    def another_private_bar
      puts "bar"
    end
  end
  public
  def instance_bar
    self.class.private_bar
  end
  def instance_bar2
    self.class.another_private_bar
  end
end

f=Foo.new
f=instance_bar # NoMethodError: private method `private_bar' called for Foo:Class
f=instance_bar2 # NoMethodError: private method `another_private_bar' called for Foo:Class

我看不到解决这个问题的方法。该文档说您不能指定私有方法的接收。同样，您只能从同一实例访问私有方法。 Foo类与给定的Foo实例是一个不同的对象。

I don't see a way to get around this. The documentation says that you cannot specify the receive of a private method. Also you can only access a private method from the same instance. The class Foo is a different object than a given instance of Foo.

别把我的答案当作定论。我当然不是专家，但是我想提供一个代码段，以便其他尝试回答的人将拥有正确的私有类方法。

Don't take my answer as final. I'm certainly not an expert, but I wanted to provide a code snippet so that others who attempt to answer will have properly private class methods.

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