From: Nate <n8agrin@...>
Date: 2009-08-25T00:30:29+09:00
Subject: Modules setting values to nil in unprocessed conditional blocks?

Hi everyone.  We're noticing some strange behavior when including
modules in classes.  It seems that even if a conditional block is
forced to evaluate as false (and presumably not execute), assignments
in the conditional block are executed and set to nil.  Here is an
example:

==========================
module Conundrum
  def riddle
    @riddle ||= 'mystery'
  end

  def riddle=(new_val)
    puts "Called riddle="
    @riddle = new_val
  end
end

class Test
  include Conundrum

  def test
    puts "Before: #{riddle}"
    if true == false
        riddle = 'solved!'
    end
    puts "After: #{riddle}"
    puts "After class: #{riddle.class}"
  end
end

Test.new.test
==========================

Note that this prints out:

Before: mystery
After:
After class: NilClass

So it would seem that riddle= is not getting called, but yet the
riddle function now returns nil.  Interestingly, this fixes the
problem:

==========================
module Conundrum
  def riddle
    @riddle ||= 'mystery'
  end

  def riddle=(new_val)
    puts "Called riddle="
    @riddle = new_val
  end
end

class Test
  include Conundrum

  def test
    puts "Before: #{riddle}"
    if true == false
        @riddle = 'solved!'
    end
    puts "After: #{riddle}"
    puts "After class: #{riddle.class}"
  end
end

Test.new.test
==========================

Outputs:

Before: mystery
After: mystery
After class: String

Any insights are much appreciated!

-n8