std.pattern.. templated publisher subscriber pattern, adding events to collections

[BLS]

Okay a  bit better snippet than before. snippet should be almost 
functional..

/*
Hi,
Andrei brings in the idea of std.pattern. Seems that this module is
"stalled";  Unfortunately !
However I would like to enhance collection classes (likewise
dcollections)  with a Publisher - Subscriber pattern (signal - slot, or
observer pattern) , if you prefer)
Hope the idea of enhancing collections with events become clear with the
following snippet.
!!! I am able to spend just a few hours a month with D programming.. in
other words, please don't kill me :)
Untested Draft code which requires a lot of help and ,more important,
feedback from you.

*/

struct publisherMsg(T) {
	T data;
	Action a;
}

mixin template Publisher(T) {
private :

	enum Action = {INSERT, UPDATE, DELETE, READONLY};	
	//alias typeof(this) PT;

	struct receiver {
		Object o;
		callback cb;	
	}

	receiver[] subscriber;
		
	publisherMsg!(T) msg;
	
	alias void delegate(const ref msg) callback;		
	
	void addSubscriber(object o, callback cb) {
		//subscriber ~= o;
	}	
	
	void publish() {
		foreach  (object o ; subscriber)
		{
		// create message and send message

		}
	}	
}

mixin template Subscriber() {
   // see UndoList for implementation	
}

final class Stack(T, bool observable = false ) {
	T[] data;	
	
	static if (observable)	mixin Observable!T;

	void push( T t) {
		data ~= t;
		publish(t, Action.INSERT);	
	}
	T pop() {
		publish(t, Action.DELETE);
		//...
	}	
	bool empty() {
		
	}
	T top() {
		publish(t, Action.READONLY);
		//...
	}
	size_t size() {

	}
}
// Undo list will receive every pushed or popped item -data and action)
class UndoList(T) {
	private:
	T[] data;
	
	/// should be part of the sunscriber mixin templates.
	publisherMsg!T stackMessage;

	void delegate(const ref stackMessage) dg;
	
	alias Stack!(int) IntegerStack;
	
	IntegerStack intstack = new IntegerStack;
		
	private this() {
		dg = &this.feedback;
		
		// SUBBSCRIBE Stack(T) push and pop events.
		intstack.addSubscriber(this, dg);
		
	}
	public void feedback(const ref stackMessage msg ) {
		writefln("Action");
	}
}