Handling exceptions raised in a Ruby thread

Question

I am looking for a solution of classic problem of exception handling. Consider following piece of code:

def foo(n)
  puts \" for #{n}\"
  sleep n
  raise \"a         


        

Answer 1

This will wait for the first thread to either raise or return (and re-raise):

require 'thwait'
def wait_for_first_block_to_complete(*blocks)
  threads = blocks.map do |block|
    Thread.new do
      block.call
    rescue StandardError
      $!
    end
  end
  waiter = ThreadsWait.new(*threads)
  value = waiter.next_wait.value
  threads.each(&:kill)
  raise value if value.is_a?(StandardError)
  value
end