Using 'return' in a Ruby block

Question

I\'m trying to use Ruby 1.9.1 for an embedded scripting language, so that \"end-user\" code gets written in a Ruby block. One issue with this is that I\'d like the users to

Answer 1

I believe this is the correct answer, despite the drawbacks:

def return_wrap(&block)
  Thread.new { return yield }.join
rescue LocalJumpError => ex
  ex.exit_value
end

def thing(*args, &block)
  value = return_wrap(&block)
  puts "value=#{value}"
end

thing {
  return 6 * 7
}

This hack allows users to use return in their procs without consequences, self is preserved, etc.

The advantage of using Thread here is that in some cases you won't get the LocalJumpError - and the return will happen in the most unexpected place (onside a top-level method, unexpectedly skipping the rest of it's body).

The main disadvantage is the potential overhead (you can replace the Thread+join with just the yield if that's enough in your scenario).