Ruby - instance variable as class variable

Question

I have a class:

class Foo

  def self.test
    @test
  end

  def foo
    @test = 1
    bar
  end

  private

  def bar
    @test = 2
  end
end

object = Foo.new.foo
Foo.test

# => nil

The only way I could get it to output '2' is by making @test a class variable. Is there any other way around using the instance variable and being able to display it with Foo.test?

Foo.test which is a class method has no access to instance variables. — Ho Man
– Ho Man, Commented Jul 15, 2017 at 10:24
What's your real goal? You're using different objects, so they obviously don't have access to the same instance variables. — Eric Duminil
– Eric Duminil, Commented Jul 15, 2017 at 10:52

Eric Duminil · Accepted Answer · 2017-07-15 10:56:38Z

1

It's not really clear to me what you want to achieve, and why. Here's an example with a "class instance variable". It might be what you're looking for:

class Foo
  class << self
    attr_accessor :test
  end

  attr_accessor :test

  def foo
    @test = 1
    bar
  end

  private

  def bar
    Foo.test = 2
  end
end

foo = Foo.new
foo.foo
p foo.test
#=> 1
p Foo.test
#=> 2

answered Jul 15, 2017 at 10:56

Eric Duminil

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1 Comment

YoloSnake Over a year ago

You commented at the same time with me lol. Well that was the purpose of the question, how to avoid using @@ but having the same result. My version is a little bit different though.

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