Observer (Publisher).ipynb

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   "source": [
    "class Subject:\n",
    "    def __init__(self):\n",
    "        self._observers = []\n",
    "\n",
    "    def attach(self, observer):\n",
    "        self._observers.append(observer)\n",
    "\n",
    "    def detach(self, observer):\n",
    "        self._observers.remove(observer)\n",
    "\n",
    "    def notify(self):\n",
    "        for observer in self._observers:\n",
    "            observer.update(self)\n",
    "\n",
    "class Observer:\n",
    "    def update(self, subject):\n",
    "        pass\n",
    "\n",
    "class ConcreteObserver(Observer):\n",
    "    def update(self, subject):\n",
    "        print(f\"Subject {id(subject)} has been updated\")\n",
    "\n",
    "class ConcreteSubject(Subject):\n",
    "    def __init__(self):\n",
    "        super().__init__()\n",
    "        self._state = None\n",
    "\n",
    "    def get_state(self):\n",
    "        return self._state\n",
    "\n",
    "    def set_state(self, state):\n",
    "        self._state = state\n",
    "        self.notify()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Subject 1606222143296 has been updated\n",
      "Subject 1606222143296 has been updated\n"
     ]
    }
   ],
   "source": [
    "subject = ConcreteSubject()\n",
    "observer1 = ConcreteObserver()\n",
    "observer2 = ConcreteObserver()\n",
    "\n",
    "subject.attach(observer1)\n",
    "subject.attach(observer2)\n",
    "\n",
    "subject.set_state(\"Sunny\")"
   ]
  }
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