By default, when you create a namespace in Needle, the namespace is registered as a service. The type of the service is determined by the @:namespace_impl_factory@ service, which (by default) returns the @Needle::Container@ class.

You can specify your own custom implementation for namespaces by registering your own @:namespace_impl_factory@ service. In fact, each namespace can have its own implementation of subnamespaces--just register a @:namespace_impl_factory@ in each one that you want to be specialized.

Here's a contrived example. Suppose you want each namespace to keep track of the precise time that it was created.

<pre>
  class TimeTrackerNamespace < Needle::Container
    attr_reader :birth_date

    def initialize( *args )
      super
      @birth_date = Time.now
    end
  end

  reg = Needle::Registry.new
  reg.register( :namespace_impl_factory ) { TimeTrackerNamespace }

  reg.namespace :hello
  p reg.hello.birth_date
</pre>

In general, you'll be better off having your custom implementation extend @Needle::Container@, although the only _real_ requirement is that your implementation publish the same interface as the default namespace implementation.
