ThreadGroup provides a means of keeping track of a number of threads as a group.

A given Thread object can only belong to one ThreadGroup at a time; adding a thread to a new group will remove it from any previous group.

Newly created threads belong to the same group as the thread from which they were created.


Adds the given thread to this group, removing it from any other group to which it may have previously been a member.

puts "Initial group is #{ThreadGroup::Default.list}"
tg = ThreadGroup.new
t1 = Thread.new { sleep }
t2 = Thread.new { sleep }
puts "t1 is #{t1}"
puts "t2 is #{t2}"
tg.add(t1)
puts "Initial group now #{ThreadGroup::Default.list}"
puts "tg group now #{tg.list}"

This will produce:

Initial group is #<Thread:0x401bdf4c>
t1 is #<Thread:0x401b3c90>
t2 is #<Thread:0x401b3c18>
Initial group now #<Thread:0x401b3c18>#<Thread:0x401bdf4c>
tg group now #<Thread:0x401b3c90>

Prevents threads from being added to or removed from the receiving ThreadGroup.

New threads can still be started in an enclosed ThreadGroup.

ThreadGroup::Default.enclose        #=> #<ThreadGroup:0x4029d914>
thr = Thread.new { Thread.stop }    #=> #<Thread:0x402a7210 sleep>
tg = ThreadGroup.new                #=> #<ThreadGroup:0x402752d4>
tg.add thr
#=> ThreadError: can't move from the enclosed thread group

Returns true if the thgrp is enclosed. See also ThreadGroup#enclose.

Returns an array of all existing Thread objects that belong to this group.

ThreadGroup::Default.list   #=> [#<Thread:0x401bdf4c run>]