Proper way to access a variable within a module while in parent module

Question

Let's say for instance I have the following case:

module A
  module B

    def self.make
      @correlation_id ||= SecureRandom.uuid
    end

  end
end

Now, for the outside world, I only want them to be able to access correlation_id through module A:

A.correlation_id. How would I access @correlation_id from module A?

I did the following, and it worked, but had a side-effect I didn't want.

module A
  module B

    def self.make
      @correlation_id ||= SecureRandom.uuid
    end

    private

    def self.correlation_id
      @correlation_id
    end
  end

  def self.correlation_id
    A::B.correlation_id
  end
end

With that in place, after I do A::B.make, I could do A.correlation_id, but sadly I am also able to do A::B.correlation_id. How would I alleviate this issue?

sawa · Accepted Answer · 2014-07-18 23:31:54Z

1

module A
  module B
    def self.make
      @correlation_id ||= SecureRandom.uuid
    end
  end
  def self.correlation_id
    B.instance_variable_get("@correlation_id")
  end
end

For efficiency, put .freeze after "@correlation_id".

answered Jul 18, 2014 at 23:31

sawa

169k51 gold badges288 silver badges401 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

David Over a year ago

This seems a bit meta. I'll definitely do this, but is there a more standard way? Just curious :)

sawa Over a year ago

What you are attempting is not standard in the first place (Allowing A to access A::B's class instance variable without allowing A::B to do so is against OOP), so there is no standard way.

David Over a year ago

Why would .freeze make this more efficient?

sawa Over a year ago

Because the string will then be only created at parse time and reused. It is a feature introduced recently.

Collectives™ on Stack Overflow

Proper way to access a variable within a module while in parent module

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related