[cells-devel] chat-server using cells?

[Lars Rune Nøstdal]

Hi,
I'm trying to figure out how to design a chat-server using Cells. This
doesn't work, but this is what I've come up with:


(defpackage CellsChat
  (:use :cl :cells))
(in-package :CellsChat)


(defparameter *newline* (princ-to-string #\Newline))



(defmodel CellsChat ()
  ((username :cell nil :accessor username-of :initarg :username
             :initform (error "CellsChat needs a `username'."))

   (text-box :accessor text-box-of :allocation :class
             :initform (c-in ""))

   (participants :cell nil :accessor participants-of :allocation :class
                 :initform nil)))



(defmethod initialize-instance :after ((chat CellsChat) &key)
  ;; New user joins the conversation.
  (push chat (participants-of chat))
  ;; New user wants to see what's been going on recently.
  (updateTextBox chat))



(defmethod updateTextBox ((chat CellsChat))
  ;; Show conversation till now.
  (format t "(text-box-of ~A): '~A'~%"
          (username-of chat)
          (text-box-of chat)))



(defobserver text-box ((chat CellsChat))
  ;; Update interface of each participant whenever
  ;; `text-box' changes (for whatever reason).
  (dolist (participant (participants-of chat))
    (updateTextBox participant)))



(defmethod say ((chat CellsChat) (what string))
  (setf (text-box-of chat)
        (concatenate 'string
                     (text-box-of chat)
                     (username-of chat) ": " what *newline*)))



(defmethod part ((chat CellsChat))
  ;; User leaves the conversation.
  (setf (participants-of chat)
        (delete chat (participants-of chat))))


-- 
Mvh,
Lars Rune Nøstdal
http://lars.nostdal.org/