From: Joel VanderWerf <vjoel@...>
Date: 2007-06-08T04:26:14+09:00
Subject: Re: raise problem in Thread

Oliver Peng wrote:
> Hi Joel:
> 
> Thank you for your reply.
> 
> One thing I am a little confused is that the main thread continues 
> executing the puts "hello". From my point of view, puts "hello" is part 
> of method test_raise. So after the exception was raised and the MyThread 
> instance was dead, the method should stopping running and just return 
> nil to main thread. Why main thread need to continue running left part 
> of this method? This can cause some unexpecting problems.

Even if a thread is dead, it still responds to methods. It's still an 
object, and all objects have a (private) #puts method that they inherit 
from Kernel.

This is actually very useful behavior:

th = Thread.new do
   1+2 # or some long computation
end

sleep 0.1
p th.alive?   # ==> false
p th.value    # ==> 3

The thread is dead, but you can retrieve the result. (If you call 
Thread#value before the thread has finished, then it waits for it to 
finish.)

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407