The multicast service is parameterized. Just send it a list of objects (i.e., other services) that you want multicasted to, and it will return a new multicaster object.

<pre>
  reg = Needle::Registry.define do |b|
    b.require 'needle/extras/multicast', 'Needle::Extras::Multicast'

    b.foo { "hello" }
    b.bar { [ 1, 2, 3 ] }
    b.baz { "test" }

    b.multicaster { |c,| c.multicast c.foo, c.bar, c.baz }
  end
</pre>

Once you've registered your service, you can send messages to the observing services by sending messages to the multicaster:

<pre>
  m = reg.multicaster
  p m.length #-> [ 5, 3, 4 ]
</pre>

The multicaster will return an array of the return values of all of the observing services. Thus, in the above example, an array of the lengths of each of the @foo@, @bar@, and @baz@ services is returned.
