try.rb

class Enumerator
  def try(exception = StandardError)
    return self unless block_given?
    yield self.next
  rescue exception => e
    @last_try = e and retry unless e.is_a? StopIteration
    raise @last_try
  end
end

3.times.try do |i|
  puts "foo #{i}"
  raise "bah"
end
# foo 0
# foo 1
# foo 2
# RuntimeError: bah

3.times.try do |i|
  puts "foo #{i}"
end
# foo 0
#  => nil

Why the @last_try ivar?

rescue exception => e
  retry unless e.is_a? StopIteration
  raise e
end

Ah, just saw your tweet—

we have to raise an exception if you’re beyond your try limit, and self.next raises StopIteration so we store the “real” exception