Ruby: accessing a class constant for instance of class

Question

I have a class that looks like the following:

class Foo
  MY_CONST = "hello"
  ANOTHER_CONST = "world"

  def self.get_my_const
    Object.const_get("ANOTHER_CONST")
  end
end

class Bar < Foo
  def do_something
    avar = Foo.get_my_const # errors here
  end
end

Getting a const_get uninitialized constant ANOTHER_CONST (NameError)

Assuming I'm just doing something silly in as far as Ruby scope goes. I'm currently using Ruby 1.9.3p0 on the machine where I'm testing this code.

Answer 1

Now working:

class Foo
  MY_CONST = "hello"
  ANOTHER_CONST = "world"

  def self.get_my_const
    const_get("ANOTHER_CONST")
  end
end

class Bar < Foo
  def do_something
    avar = Foo.get_my_const
  end
end

Bar.new.do_something # => "world"

Your below part is not correct:

def self.get_my_const
    Object.const_get("ANOTHER_CONST")
end

Inside the method get_my_const,self is Foo. So remove Object,it will work..

Answer 2

You can use const like:

Foo::MY_CONST
Foo::ANOTHER_CONST

You can gey a array of constants:

Foo.constants
Foo.constants.first

With your code:

class Foo
    MY_CONST = 'hello'

    def self.get_my_const
        Foo::MY_CONST
    end
end


class Bar < Foo
    def do_something
        avar = Foo.get_my_const
    end
end


x = Bar.new
x.do_something