sleep until condition is true in ruby

Question

Is there any better way in Ruby to sleep until some condition is true ?

loop do 
  sleep(1)
  if ready_to_go
    break
  end
end

Answer 1

You can use the waitutil gem as described at http://rubytools.github.io/waitutil/, e.g.

require 'waitutil'

WaitUtil.wait_for_condition("my_event to happen", 
                            :timeout_sec => 30,
                            :delay_sec => 0.5) do
  check_if_my_event_happened
end

Answer 2

I like this form since it is simple and only uses sleep if needed after it tests for the done condition:

begin
  ready_to_go = do_some_action
end until ready_to_go or not sleep 1

Answer 3

until can be a statement modifier, leading to:

sleep(1) until ready_to_go

You'll have to use that in a thread with another thread changing ready_to_go otherwise you'll hang.

while (!ready_to_go)
  sleep(1)
end

is similar to that but, again, you'd need something to toggle ready_to_go or you'd hang.

You could use:

until (ready_to_go)
  sleep(1)
end

but I've never been comfortable using until like that. Actually I almost never use it, preferring the equivalent (!ready_to_go).

Answer 4

def sleep_until(time)
  time.times do
    break if block_given? && yield
    sleep(1)
  end
end

Usage:

sleep_until(18){till_i_die}