Ruby scope, returning a Proc from a function

Question

Coming from a JavaScript background I've become accustomed to being able to use JavaScript's dynamic scope to encapsulate values in a function. For example:

function Dog( firstname, lastname ) {

  this.fullname = firstname + lastname

  return {
    say_name: function () {
      return fullname;
    }
  }

}

Now in Ruby I'm not so sure something like this would work too well:

class Foo

  attr_accessor :bar, :baz

  def initialize bar, baz
    @bar = bar
    @baz = baz
  end

  def give_me_a_proc
    return Proc.new { @bar + @baz }
  end
end

Can anyone give a quick explanation of how scope works in Ruby? If I call the Proc returned from give_me_a_proc, will it still have access to its define-time scope?

Also do the values become fixed once I define the proc or do any changes made in Foo get carried down to the Proc even after it has been defined?

Answer 1

Yes, it will still have access to definition time scope. See documentation for Proc class.

Changes are carried down to the Proc post-definition. Results from irb run with your class.

> foo = Foo.new(1, 2)
 => #<Foo:0x007f9002167080 @bar=1, @baz=2> 
> quux = foo.give_me_a_proc
 => #<Proc:0x007f900214f688@(irb):11> 
> quux.call
 => 3 
> foo.bar = 3
 => 3 
> quux.call
 => 5