ThreadGroup provides a means of keeping track of a number of threads as a group. A Thread can belong to only 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.

Methods
A
E
L
Constants
Default = th->thgroup
 

The default ThreadGroup created when Ruby starts; all Threads belong to it by default.
Instance Public methods
thgrp.add(thread) → thgrp

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

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}"

produces:

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>

Source: show 

static VALUE
thgroup_add(VALUE group, VALUE thread)
{
    rb_thread_t *th;
    struct thgroup *data;

    rb_secure(4);
    GetThreadPtr(thread, th);

    if (OBJ_FROZEN(group)) {
        rb_raise(rb_eThreadError, "can't move to the frozen thread group");
    }
    TypedData_Get_Struct(group, struct thgroup, &thgroup_data_type, data);
    if (data->enclosed) {
        rb_raise(rb_eThreadError, "can't move to the enclosed thread group");
    }

    if (!th->thgroup) {
        return Qnil;
    }

    if (OBJ_FROZEN(th->thgroup)) {
        rb_raise(rb_eThreadError, "can't move from the frozen thread group");
    }
    TypedData_Get_Struct(th->thgroup, struct thgroup, &thgroup_data_type, data);
    if (data->enclosed) {
        rb_raise(rb_eThreadError,
                 "can't move from the enclosed thread group");
    }

    th->thgroup = group;
    return group;
}
thgrp.enclose → thgrp

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

produces:

ThreadError: can't move from the enclosed thread group

Source: show 

static VALUE
thgroup_enclose(VALUE group)
{
    struct thgroup *data;

    TypedData_Get_Struct(group, struct thgroup, &thgroup_data_type, data);
    data->enclosed = 1;

    return group;
}
thgrp.enclosed? → true or false

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

Source: show 

static VALUE
thgroup_enclosed_p(VALUE group)
{
    struct thgroup *data;

    TypedData_Get_Struct(group, struct thgroup, &thgroup_data_type, data);
    if (data->enclosed)
        return Qtrue;
    return Qfalse;
}
thgrp.list → array

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

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

Source: show 

static VALUE
thgroup_list(VALUE group)
{
    VALUE ary = rb_ary_new();
    struct thgroup_list_params param;

    param.ary = ary;
    param.group = group;
    st_foreach(GET_THREAD()->vm->living_threads, thgroup_list_i, (st_data_t) & param);
    return ary;
}