{"id":1502,"date":"2023-10-13T16:06:45","date_gmt":"2023-10-13T14:06:45","guid":{"rendered":"https:\/\/epicmarketing.co.il\/notebook\/?p=1502"},"modified":"2023-10-14T20:49:54","modified_gmt":"2023-10-14T18:49:54","slug":"the-observer-design-pattern","status":"publish","type":"post","link":"https:\/\/epicmarketing.co.il\/notebook\/the-observer-design-pattern\/","title":{"rendered":"The Observer Design Pattern"},"content":{"rendered":"\n

The Observer Design Pattern \u05de\u05d2\u05d3\u05d9\u05e8 \u05e2\u05d1\u05d5\u05e8\u05e0\u05d5 \u05d9\u05d7\u05e1\u05d9\u05dd \u05e9\u05dc \u05d9\u05d7\u05d9\u05d3 \u05dc\u05e8\u05d1\u05d9\u05dd \u05d1\u05d9\u05df \u05d0\u05d5\u05d1\u05d9\u05d9\u05e7\u05d8\u05d9\u05dd, \u05db\u05da \u05e9\u05db\u05e9\u05de\u05ea\u05d1\u05e6\u05e2 \u05e9\u05d9\u05e0\u05d5\u05d9 \u05d1\u05d0\u05d5\u05d1\u05d9\u05d9\u05e7\u05d8 \u05e9\u05d0\u05e0\u05d7\u05e0\u05d5 \u05e2\u05d5\u05e7\u05d1\u05d9\u05dd \u05d0\u05d7\u05e8\u05d9\u05d5, \u05db\u05dc \u05d4\u05ea\u05dc\u05d5\u05d9\u05d9\u05dd \u05d1\u05d5 \u05d9\u05e7\u05d1\u05dc\u05d5 \u05d4\u05d5\u05d3\u05e2\u05d4 \u05d5\u05d9\u05ea\u05e2\u05d3\u05db\u05e0\u05d5.<\/p>\n\n\n\n

\u05de\u05d4 \u05d6\u05d4 Observer Design Pattern?<\/h2>\n\n\n\n

\u05e0\u05e0\u05d9\u05d7 \u05e9\u05d9\u05e9 \u05dc\u05db\u05dd \u05e2\u05e8\u05d5\u05e5 \u05d9\u05d5\u05d8\u05d9\u05d5\u05d1. \u05d1\u05db\u05dc \u05e4\u05e2\u05dd \u05db\u05e9\u05d0\u05ea\u05dd \u05de\u05e2\u05dc\u05d9\u05dd \u05d5\u05d9\u05d3\u05d0\u05d5, \u05db\u05dc \u05d4\u05de\u05e0\u05d5\u05d9\u05d9\u05dd \u05e9\u05dc\u05db\u05dd \u05de\u05e7\u05d1\u05dc\u05d9\u05dd \u05d4\u05d5\u05d3\u05e2\u05d4. \u05d4\u05e2\u05e8\u05d5\u05e5 \u05e9\u05dc\u05db\u05dd "\u05e0\u05e6\u05e4\u05d4" \u05e2\u05dc \u05d9\u05d3\u05d9 \u05d4\u05de\u05e0\u05d5\u05d9\u05d9\u05dd \u05e9\u05d4\u05dd "\u05e6\u05d5\u05e4\u05d9\u05dd". \u05db\u05e9\u05de\u05e2\u05dc\u05d9\u05dd \u05e1\u05e8\u05d8\u05d5\u05df \u05d7\u05d3\u05e9, \u05db\u05dc\u05d5\u05de\u05e8 \u05db\u05e9\u05d9\u05e9 \u05e9\u05d9\u05e0\u05d5\u05d9 \u05d1"\u05de\u05e6\u05d1" \u05e9\u05dc \u05d4\u05e2\u05e8\u05d5\u05e5, \u05db\u05dc \u05d4\u05de\u05e0\u05d5\u05d9\u05d9\u05dd observers \u05de\u05e7\u05d1\u05dc\u05d9\u05dd \u05d4\u05d5\u05d3\u05e2\u05d4.<\/p>\n\n\n

\n
\"\"<\/figure>\n<\/div>\n\n\n

\u05d0\u05dd \u05e0\u05e4\u05e8\u05e7 \u05d0\u05ea \u05d4\u05d3\u05d5\u05d2\u05de\u05d0 \u05de\u05dc\u05de\u05e2\u05dc\u05d4 \u05dc\u05de\u05d5\u05e0\u05d7\u05d9\u05dd \u05e9\u05dc Observer Design Pattern, \u05d9\u05e9 \u05dc\u05e0\u05d5:<\/p>\n\n\n\n

Subject<\/strong> – \u05e2\u05e8\u05d5\u05e5 \u05d4\u05d9\u05d5\u05d8\u05d9\u05d5\u05d1 – \u05de\u05d4 \u05e9\u05d0\u05e0\u05d7\u05e0\u05d5 \u05e6\u05d5\u05e4\u05d9\u05dd \u05d1\u05e9\u05d9\u05e0\u05d5\u05d9\u05d9\u05dd \u05e9\u05dc\u05d5. \u05d4\u05d5\u05d0 \u05de\u05d7\u05d6\u05d9\u05e7 \u05e8\u05e9\u05d9\u05de\u05d4 \u05e9\u05dc \u05de\u05e0\u05d5\u05d9\u05d9\u05dd observers \u05d5\u05de\u05d5\u05d3\u05d9\u05e2 \u05dc\u05d4\u05dd \u05db\u05e9\u05d9\u05e9 \u05d1\u05d5 \u05e9\u05d9\u05e0\u05d5\u05d9.<\/p>\n\n\n\n

Observers<\/strong> – \u05d4\u05de\u05e0\u05d5\u05d9\u05d9\u05dd – \u05d4\u05dd \u05de\u05e0\u05d5\u05d9\u05d9\u05dd \u05dc-Subject<\/strong> \u05d5\u05e8\u05d5\u05e6\u05d9\u05dd \u05dc\u05d1\u05e6\u05e2 \u05d0\u05d9\u05d6\u05d4 \u05e4\u05e2\u05d5\u05dc\u05d4 \u05db\u05d0\u05e9\u05e8 \u05d9\u05d4\u05d9\u05d4 \u05d1\u05d5 \u05e9\u05d9\u05e0\u05d5\u05d9.<\/p>\n\n\n\n

\u05d1\u05de\u05d5\u05e9\u05d2\u05d9\u05dd \u05e9\u05dc \u05e2\u05d5\u05dc\u05dd \u05d4\u05e4\u05d9\u05ea\u05d5\u05d7, \u05d9\u05e9 \u05dc\u05e0\u05d5:<\/p>\n\n\n\n

Subject<\/strong> – \u05d4-class \u05e9\u05d9\u05e9 \u05d1\u05d5 \u05e4\u05d5\u05e0\u05e7\u05e6\u05d9\u05d5\u05ea \u05e9\u05dc add, remove \u05e9\u05dc observers, \u05d5\u05e4\u05d5\u05e0\u05e7\u05e6\u05d9\u05d4 \u05e9\u05de\u05d5\u05e6\u05d9\u05d0\u05d4 \u05d0\u05ea \u05d4\u05d4\u05d5\u05d3\u05e2\u05d5\u05ea \u05dc\u05de\u05e0\u05d5\u05d9\u05d9\u05dd \u05db\u05e9\u05d9\u05e9 \u05e9\u05d9\u05e0\u05d5\u05d9 \u05d1\u05de\u05e6\u05d1.<\/p>\n\n\n\n

Observer<\/strong> – \u05dc-classes \u05d4\u05d0\u05dc\u05d4 \u05d9\u05e9 \u05e4\u05d5\u05e0\u05e7\u05e6\u05d9\u05d4 \u05e9\u05e0\u05e7\u05e8\u05d0\u05ea \u05db\u05d0\u05e9\u05e8 \u05d9\u05e9 \u05e9\u05d9\u05e0\u05d5\u05d9 \u05d1-Subject<\/strong>.<\/p>\n\n\n\n

\u05d3\u05d5\u05d2\u05de\u05d0 – \u05ea\u05d7\u05e0\u05ea \u05de\u05d6\u05d2 \u05d0\u05d5\u05d9\u05e8<\/h2>\n\n\n\n

\u05e0\u05e7\u05d7 \u05dc\u05d3\u05d5\u05d2\u05de\u05d0 \u05d0\u05e4\u05dc\u05d9\u05e7\u05e6\u05d9\u05d4 \u05e9\u05dc \u05de\u05d6\u05d2 \u05d0\u05d5\u05d9\u05e8 (subject). \u05d4\u05d0\u05e4\u05dc\u05d9\u05e7\u05e6\u05d9\u05d4 \u05d0\u05d5\u05e1\u05e4\u05ea \u05de\u05d9\u05d3\u05e2 \u05de\u05de\u05e1\u05e4\u05e8 \u05e1\u05e0\u05e1\u05d5\u05e8\u05d9\u05dd \u05d5\u05de\u05e6\u05d9\u05d2\u05d4 \u05d0\u05ea \u05de\u05d6\u05d2 \u05d4\u05d0\u05d5\u05d9\u05e8 \u05d4\u05de\u05e2\u05d5\u05d3\u05db\u05df.<\/p>\n\n\n\n

\u05d4\u05de\u05e9\u05ea\u05de\u05e9\u05d9\u05dd \u05d1\u05d0\u05e4\u05dc\u05d9\u05e7\u05e6\u05d9\u05d4 \u05de\u05e7\u05d1\u05dc\u05d9\u05dd \u05d4\u05ea\u05e8\u05e2\u05d5\u05ea (observers) \u05db\u05d0\u05e9\u05e8 \u05d9\u05e9 \u05ea\u05e0\u05d0\u05d9\u05dd \u05de\u05e1\u05d5\u05d9\u05d9\u05de\u05d9\u05dd \u05dc\u05de\u05d6\u05d2 \u05d4\u05d0\u05d5\u05d9\u05e8. \u05dc\u05de\u05e9\u05dc:<\/p>\n\n\n\n

    \n
  • \u05e6\u05e4\u05d5\u05d9 \u05d2\u05e9\u05dd.<\/li>\n\n\n\n
  • \u05d4\u05d8\u05de\u05e4\u05e8\u05d8\u05d5\u05e8\u05d4 \u05d9\u05d5\u05e8\u05d3\u05ea \u05de\u05ea\u05d7\u05ea \u05dc-0 \u05de\u05e2\u05dc\u05d5\u05ea.<\/li>\n<\/ul>\n\n\n\n

    \u05e2\u05dd Observer Design Pattern, \u05d4\u05d0\u05e4\u05dc\u05d9\u05e7\u05e6\u05d9\u05d4 \u05dc\u05d0 \u05e6\u05e8\u05d9\u05db\u05d4 \u05dc\u05d3\u05e2\u05ea \u05d0\u05ea \u05d4\u05e4\u05e8\u05d8\u05d9\u05dd \u05e9\u05dc \u05d4\u05de\u05e9\u05ea\u05de\u05e9\u05d9\u05dd. \u05d4\u05d9\u05d0 \u05e9\u05d5\u05dc\u05d7\u05ea \u05d0\u05ea \u05d4\u05de\u05d9\u05d3\u05e2 \u05dc\u05db\u05dc \u05de\u05d9 \u05e9\u05e8\u05e9\u05d5\u05dd \u05dc\u05e9\u05d9\u05e8\u05d5\u05ea \u05e9\u05dc\u05d4.<\/p>\n\n\n

    \n
    \"\"<\/figure>\n<\/div>\n\n\n

    \u05d4\u05d7\u05dc\u05e7\u05d9\u05dd \u05e9\u05dc \u05d4\u05e4\u05e2\u05d5\u05dc\u05d4 \u05d4\u05dd:<\/p>\n\n\n\n

    Weather Station App (Subject)<\/strong> – \u05d0\u05d5\u05e1\u05e4\u05ea \u05d0\u05ea \u05d4\u05de\u05d9\u05d3\u05e2, \u05de\u05d5\u05d3\u05d9\u05e2\u05d4 \u05dc\u05de\u05d9 \u05e9\u05e8\u05e9\u05d5\u05dd \u05d0\u05dc\u05d9\u05d4.<\/p>\n\n\n\n

    Notifications\/Alerts (Observers)<\/strong> – \u05de\u05d7\u05db\u05d9\u05dd \u05dc\u05e2\u05d3\u05db\u05d5\u05e0\u05d9\u05dd, \u05de\u05ea\u05d1\u05e6\u05e2\u05ea \u05e4\u05e2\u05d5\u05dc\u05d4 \u05db\u05d0\u05e9\u05e8 \u05de\u05d2\u05d9\u05e2 \u05d4\u05e2\u05d3\u05db\u05d5\u05df.<\/p>\n\n\n\n

    \u05e0\u05e8\u05d0\u05d4 \u05d0\u05d9\u05da \u05d6\u05d4 \u05d9\u05e8\u05d0\u05d4 \u05d1\u05e7\u05d5\u05d3.<\/p>\n\n\n

    \nclass WeatherStation {\n    constructor() {\n        this.observers = [];\n        this.weatherData = { temperature: 0, humidity: 0, pressure: 0 };\n    }\n\n    addObserver(observer) {\n        this.observers.push(observer);\n    }\n\n    removeObserver(observer) {\n        const index = this.observers.indexOf(observer);\n        if (index > -1) {\n            this.observers.splice(index, 1);\n        }\n    }\n\n    notifyObservers() {\n        for (const observer of this.observers) {\n            observer.update(this.weatherData);\n        }\n    }\n\n    setWeatherData(newWeatherData) {\n        this.weatherData = { ...this.weatherData, ...newWeatherData };\n        this.notifyObservers();\n    }\n}\n\nclass WeatherAlert {\n    constructor(alertType) {\n        this.alertType = alertType;\n    }\n\n    update(weatherData) {\n        \/\/ Basic demonstration: you might have more complex logic here in a real app\n        console.log(`Weather Alert [${this.alertType}]: \n           New weather data received!`, weatherData);\n    }\n}\n\n\/\/ Example usage\nconst weatherStation = new WeatherStation();\n\nconst rainAlert = new WeatherAlert("Rain");\nconst freezeAlert = new WeatherAlert("Freeze");\n\nweatherStation.addObserver(rainAlert);\nweatherStation.addObserver(freezeAlert);\n\nweatherStation.setWeatherData({ temperature: 25, humidity: 80, pressure: 1013 });\n\/\/ Weather Alert [Rain]: New weather data received! \n\/\/ { temperature: 25, humidity: 80, pressure: 1013 }\n\/\/ Weather Alert [Freeze]: New weather data received! \n\/\/ { temperature: 25, humidity: 80, pressure: 1013 }\n\nweatherStation.setWeatherData({ temperature: -1, humidity: 80, pressure: 1010 });\n\/\/ Weather Alert [Rain]: New weather data received! \n\/\/ { temperature: -1, humidity: 80, pressure: 1010 }\n\/\/ Weather Alert [Freeze]: New weather data received! \n\/\/ { temperature: -1, humidity: 80, pressure: 1010 }\n<\/pre><\/div>\n\n\n
    \u05de\u05d4 \u05d9\u05e9 \u05dc\u05e0\u05d5 \u05e4\u05d4?<\/p>\n\n\n\n
    WeatherStation (Subject)<\/span><\/strong><\/p>\n\n\n\n
      \n
    • addObserver(observer) – \u05de\u05d5\u05e1\u05d9\u05e3 observer \u05e9\u05d9\u05e7\u05d1\u05dc \u05d0\u05ea \u05d4\u05d4\u05d5\u05d3\u05e2\u05d5\u05ea.<\/li>\n\n\n\n
    • removeObserver(observer) – \u05de\u05d5\u05e8\u05d9\u05d3 observer  \u05de\u05e8\u05e9\u05d9\u05de\u05ea \u05de\u05e7\u05d1\u05dc\u05d9 \u05d4\u05d4\u05d5\u05d3\u05e2\u05d5\u05ea.<\/li>\n\n\n\n
    • notifyObservers – \u05de\u05d5\u05d3\u05d9\u05e2 \u05dc\u05db\u05dc \u05d4\u05e8\u05e9\u05d5\u05de\u05d9\u05dd \u05e2\u05dc \u05d4\u05e9\u05d9\u05e0\u05d5\u05d9\u05d9\u05dd.<\/li>\n\n\n\n
    • setWeatherData(newWeatherData) – \u05de\u05e2\u05d3\u05db\u05df \u05d0\u05ea \u05d4\u05de\u05d9\u05d3\u05e2 \u05d5\u05e9\u05d5\u05dc\u05d7 \u05d4\u05d5\u05d3\u05e2\u05d4 \u05dc\u05e0\u05e8\u05e9\u05de\u05d9\u05dd.<\/li>\n<\/ul>\n\n\n\n
      WeatherAlert (Observer)<\/span><\/strong><\/p>\n\n\n\n
        \n
      • update(weatherData) – \u05de\u05d1\u05e6\u05e2 \u05e4\u05e2\u05d5\u05dc\u05d4 \u05e2\u05dc \u05e1\u05de\u05da \u05d4\u05de\u05d9\u05d3\u05e2 \u05e9\u05d4\u05ea\u05e7\u05d1\u05dc. \u05d1\u05d0\u05e4\u05dc\u05d9\u05e7\u05e6\u05d9\u05d4 \u05d0\u05de\u05d9\u05ea\u05d9\u05ea, \u05e4\u05d4 \u05d4\u05d9\u05ea\u05d4 \u05e4\u05e2\u05d5\u05dc\u05d4 \u05e9\u05dc \u05d4\u05e6\u05d2\u05d4 \u05d0\u05d5 \u05e9\u05dc\u05d9\u05d7\u05d4 \u05e9\u05dc \u05d4\u05de\u05d9\u05d3\u05e2, \u05dc\u05de\u05e9\u05dc.<\/li>\n<\/ul>\n\n\n\n
        \u05db\u05e9\u05d9\u05e9 \u05e7\u05e8\u05d9\u05d0\u05d4 \u05dc-setWeatherData \u05d1\u05ea\u05d5\u05da WeatherStation \u05de\u05ea\u05e2\u05d3\u05db\u05df \u05d4-weatherData \u05e9\u05de\u05d5\u05d3\u05d9\u05e2 \u05dc\u05db\u05dc \u05d4\u05e0\u05e8\u05e9\u05de\u05d9\u05dd \u05e9\u05dc\u05d5 \u05e2\u05dc \u05d4\u05de\u05d9\u05d3\u05e2.<\/p>\n\n\n\n
        \u05d3\u05d5\u05d2\u05de\u05d0 \u05e0\u05d5\u05e1\u05e4\u05ea – \u05d0\u05ea\u05e8 \u05de\u05db\u05d9\u05e8\u05d5\u05ea<\/h2>\n\n\n\n
        \u05e0\u05e7\u05d7 \u05dc\u05d3\u05d5\u05d2\u05de\u05d0 \u05d0\u05ea\u05e8 \u05de\u05db\u05d9\u05e8\u05d5\u05ea. \u05e0\u05e0\u05d9\u05d7 \u05e9\u05d9\u05e9 \u05dc\u05e0\u05d5 \u05de\u05e1\u05e4\u05e8 \u05e7\u05d5\u05de\u05e4\u05d5\u05e0\u05e0\u05d8\u05d5\u05ea \u05e9\u05e6\u05e8\u05d9\u05db\u05d5\u05ea \u05dc\u05d4\u05ea\u05e2\u05d3\u05db\u05df \u05db\u05d0\u05e9\u05e8 \u05d4\u05d2\u05d5\u05dc\u05e9 \u05de\u05db\u05e0\u05d9\u05e1 \u05de\u05d5\u05e6\u05e8 \u05d7\u05d3\u05e9 \u05dc\u05e2\u05d2\u05dc\u05d4, \u05dc\u05de\u05e9\u05dc \u05e1\u05d9\u05db\u05d5\u05dd \u05e1\u05db\u05d5\u05dd \u05d4\u05e8\u05db\u05d9\u05e9\u05d4 \u05d1\u05e2\u05d2\u05dc\u05d4, \u05e8\u05e9\u05d9\u05de\u05ea \u05d4\u05de\u05d5\u05e6\u05e8\u05d9\u05dd \u05dc\u05e8\u05db\u05d9\u05e9\u05d4, \u05d1\u05d0\u05e0\u05e8\u05d9\u05dd \u05e4\u05e8\u05e1\u05d5\u05de\u05d9\u05d9\u05dd \u05d5\u05e2\u05d5\u05d3.<\/p>\n\n\n\n
        \u05e0\u05e8\u05d0\u05d4 \u05d3\u05d5\u05d2\u05de\u05d0 \u05dc\u05e7\u05d5\u05d3 \u05d0\u05e0\u05d2\u05d5\u05dc\u05e8\u05d9.<\/p>\n\n\n\n
        Cart Service (Subject)<\/span><\/strong><\/p>\n\n\n\n
        \u05d1-service \u05d0\u05e0\u05d7\u05e0\u05d5 \u05de\u05e0\u05d4\u05dc\u05d9\u05dd \u05d0\u05ea \u05d4\u05de\u05d5\u05e6\u05e8\u05d9\u05dd \u05e9\u05e0\u05de\u05e6\u05d0\u05d9\u05dd \u05d1\u05e2\u05d2\u05dc\u05d4 \u05d5\u05de\u05d7\u05d6\u05d9\u05e7\u05d9\u05dd \u05e8\u05e9\u05d9\u05de\u05d4 \u05e9\u05dc observers \u05e9\u05e6\u05e8\u05d9\u05da \u05dc\u05d4\u05d5\u05d3\u05d9\u05e2 \u05dc\u05d4\u05dd \u05db\u05e9\u05d9\u05e9 \u05d4\u05d5\u05e1\u05e4\u05d4 \u05e9\u05dc \u05de\u05d5\u05e6\u05e8.<\/p>\n\n\n
        \nimport { Injectable } from '@angular\/core';\nimport { BehaviorSubject, Observable } from 'rxjs';\n\n@Injectable({\n  providedIn: 'root'\n})\nexport class CartService {\n  private cartItems: any[] = [];\n  private cartSubject = new BehaviorSubject(this.cartItems);\n\n  addToCart(item: any): void {\n    this.cartItems.push(item);\n    this.cartSubject.next(this.cartItems);\n  }\n\n  getCartObservable(): Observable<any[]> {\n    return this.cartSubject.asObservable();\n  }\n}\n<\/pre><\/div>\n\n\n
        Cart Component (Observer)<\/span><\/strong><\/p>\n\n\n\n
        \u05d4\u05e7\u05d5\u05de\u05e4\u05d5\u05e0\u05e0\u05d8\u05d4 \u05d4\u05d6\u05d0\u05ea \u05de\u05e6\u05d9\u05d2\u05d4 \u05d0\u05ea \u05ea\u05d5\u05db\u05df \u05d4\u05e2\u05d2\u05dc\u05d4 \u05d5\u05de\u05ea\u05e2\u05d3\u05db\u05e0\u05ea \u05db\u05d0\u05e9\u05e8 \u05de\u05d5\u05db\u05e0\u05e1 \u05d0\u05dc\u05d9\u05d4 \u05de\u05d5\u05e6\u05e8 \u05d7\u05d3\u05e9.<\/p>\n\n\n
        \nimport { Component, OnInit, OnDestroy } from '@angular\/core';\nimport { CartService } from '.\/cart.service';\nimport { Subscription } from 'rxjs';\n\n@Component({\n  selector: 'app-cart',\n  template: `\n    <h2>Your Cart<\/h2>\n    <ul>\n      <li *ngFor="let item of cartItems">{{ item.name }}<\/li>\n    <\/ul>\n  `\n})\nexport class CartComponent implements OnInit, OnDestroy {\n  cartItems: any[] = [];\n  cartSubscription!: Subscription;\n\n  constructor(private cartService: CartService) {}\n\n  ngOnInit(): void {\n    this.cartSubscription = this.cartService.getCartObservable().subscribe(items => {\n      this.cartItems = items;\n    });\n  }\n\n  ngOnDestroy(): void {\n    this.cartSubscription.unsubscribe();\n  }\n}\n<\/pre><\/div>\n\n\n
        Add Product Component<\/span><\/strong><\/p>\n\n\n\n
        \u05d4\u05e7\u05d5\u05de\u05e4\u05d5\u05e0\u05e0\u05d8\u05d4 \u05d4\u05d6\u05d0\u05ea \u05de\u05d0\u05e4\u05e9\u05e8\u05ea \u05dc\u05de\u05e9\u05ea\u05de\u05e9\u05d9\u05dd \u05dc\u05d4\u05d5\u05e1\u05d9\u05e3 \u05de\u05d5\u05e6\u05e8\u05d9\u05dd.<\/p>\n\n\n
        \nimport { Component } from '@angular\/core';\nimport { CartService } from '.\/cart.service';\n\n@Component({\n  selector: 'app-add-product',\n  template: `\n    <button (click)="addItem()">Add Item to Cart<\/button>\n  `\n})\nexport class AddProductComponent {\n  constructor(private cartService: CartService) {}\n\n  addItem(): void {\n    const newItem = { name: `Item ${Math.floor(Math.random() * 100)}` };\n    this.cartService.addToCart(newItem);\n  }\n}\n<\/pre><\/div>\n\n\n
        \u05dc\u05de\u05d4 \u05dc\u05d4\u05e9\u05ea\u05de\u05e9 \u05d1-Observer Design Pattern?<\/h2>\n\n\n\n
        Decoupling – \u05d4-subject \u05dc\u05d0 \u05e6\u05e8\u05d9\u05da \u05dc\u05d3\u05e2\u05ea \u05db\u05dc\u05d5\u05dd \u05e2\u05dc \u05d4\u05e2\u05d5\u05e7\u05d1\u05d9\u05dd \u05d0\u05d7\u05e8\u05d9\u05d5.<\/p>\n\n\n\n
        Dynamic Relationships – \u05d0\u05e4\u05e9\u05e8 \u05dc\u05d4\u05d5\u05e1\u05d9\u05e3 \u05d5\u05dc\u05d4\u05d5\u05e8\u05d9\u05d3 Observers \u05d1\u05d6\u05de\u05df \u05e8\u05d9\u05e6\u05d4 \u05d1\u05dc\u05d9 \u05dc\u05e9\u05e0\u05d5\u05ea \u05d0\u05ea \u05d4\u05d0\u05d5\u05d1\u05d9\u05d9\u05e7\u05d8\u05d9\u05dd.<\/p>\n\n\n\n
        Broadcast Communication – \u05e9\u05d9\u05e0\u05d5\u05d9\u05d9\u05dd \u05d1\u05de\u05d9\u05d3\u05e2 \u05d1\u05d0\u05d5\u05d1\u05d9\u05d9\u05e7\u05d8 \u05d0\u05d7\u05d3 \u05de\u05e9\u05d5\u05d3\u05e8\u05d9\u05dd \u05dc\u05d4\u05e8\u05d1\u05d4 \u05d0\u05d5\u05d1\u05d9\u05d9\u05e7\u05d8\u05d9\u05dd \u05d0\u05d7\u05e8\u05d9\u05dd.<\/p>\n\n\n\n
        \u05d3\u05d5\u05d2\u05de\u05d0 \u05e0\u05d5\u05e1\u05e4\u05ea – \u05d0\u05d9\u05de\u05d5\u05ea \u05de\u05e9\u05ea\u05de\u05e9<\/h2>\n\n\n\n
        \u05e0\u05e8\u05d0\u05d4 \u05d3\u05d5\u05d2\u05de\u05d0 \u05d0\u05e0\u05d2\u05d5\u05dc\u05e8\u05d9\u05ea \u05e0\u05d5\u05e1\u05e4\u05ea \u05e9\u05d1\u05d4 \u05e0\u05d1\u05d7\u05df authentication \u05e9\u05dc \u05de\u05e9\u05ea\u05de\u05e9. \u05db\u05d0\u05e9\u05e8 \u05de\u05e9\u05ea\u05de\u05e9 \u05de\u05ea\u05d7\u05d1\u05e8 \u05dc\u05d7\u05e9\u05d1\u05d5\u05df \u05e9\u05dc\u05d5 \u05d9\u05d4\u05d9\u05d5 \u05de\u05e1\u05e4\u05e8 \u05e7\u05d5\u05de\u05e4\u05d5\u05e0\u05e0\u05d8\u05d5\u05ea \u05e9\u05d9\u05e6\u05d8\u05e8\u05db\u05d5 \u05dc\u05e7\u05d1\u05dc \u05d0\u05ea \u05d4\u05de\u05d9\u05d3\u05e2 \u05d4\u05d6\u05d4 \u05db\u05de\u05d5 \u05ea\u05e4\u05e8\u05d9\u05d8 \u05e8\u05d0\u05e9\u05d9, \u05ea\u05e4\u05e8\u05d9\u05d8 \u05e6\u05d3 \u05d5\u05db\u05d5'<\/p>\n\n\n\n
        AuthService (Subject)<\/span><\/strong><\/p>\n\n\n
        \nimport { Injectable } from '@angular\/core';\nimport { BehaviorSubject, Observable } from 'rxjs';\n\n@Injectable({\n  providedIn: 'root'\n})\nexport class AuthService {\n  private isAuthenticatedSubject = new BehaviorSubject<boolean>(false);\n  isAuthenticated$ = this.isAuthenticatedSubject.asObservable();\n\n  login(): void {\n    \/\/ Authentication logic (e.g., API call) would be here...\n    this.isAuthenticatedSubject.next(true);\n  }\n\n  logout(): void {\n    \/\/ Logout logic would be here...\n    this.isAuthenticatedSubject.next(false);\n  }\n}\n<\/pre><\/div>\n\n\n
        HeaderComponent (Observer)<\/span><\/strong><\/p>\n\n\n\n
        \u05d4\u05e7\u05d5\u05de\u05e4\u05d5\u05e0\u05e0\u05d8\u05d4 \u05d4\u05d6\u05d0\u05ea \u05de\u05e6\u05d9\u05d2\u05d4 \u05de\u05d9\u05d3\u05e2 \u05dc\u05d2\u05d5\u05dc\u05e9 \u05d1-header \u05d5\u05de\u05ea\u05e2\u05d3\u05db\u05e0\u05ea \u05db\u05d0\u05e9\u05e8 \u05d4\u05d2\u05d5\u05dc\u05e9 \u05e0\u05db\u05e0\u05e1 \u05dc\u05d7\u05e9\u05d1\u05d5\u05df.<\/p>\n\n\n
        \nimport { Component, OnInit, OnDestroy } from '@angular\/core';\nimport { AuthService } from '.\/auth.service';\nimport { Subscription } from 'rxjs';\n\n@Component({\n  selector: 'app-header',\n  template: `\n    <ng-container *ngIf="isAuthenticated; else loggedOutTemplate">\n      <p>Welcome, User!<\/p>\n    <\/ng-container>\n    <ng-template #loggedOutTemplate>\n      <p>Please log in.<\/p>\n    <\/ng-template>\n  `\n})\nexport class HeaderComponent implements OnInit, OnDestroy {\n  isAuthenticated: boolean = false;\n  private authSubscription!: Subscription;\n\n  constructor(private authService: AuthService) {}\n\n  ngOnInit(): void {\n    this.authSubscription = this.authService.isAuthenticated$.subscribe(\n      isAuthenticated => {\n        this.isAuthenticated = isAuthenticated;\n      }\n    );\n  }\n\n  ngOnDestroy(): void {\n    this.authSubscription.unsubscribe();\n  }\n}\n<\/pre><\/div>\n\n\n
        LoginFormComponent<\/span><\/strong><\/p>\n\n\n\n
        \u05d4\u05e7\u05d5\u05de\u05e4\u05d5\u05e0\u05e0\u05d8\u05d4 \u05de\u05d0\u05e4\u05e9\u05e8\u05ea \u05db\u05e0\u05d9\u05e1\u05d4 \u05d5\u05d9\u05e6\u05d9\u05d0\u05d4 \u05de\u05d4\u05d7\u05e9\u05d1\u05d5\u05df.<\/p>\n\n\n
        \nimport { Component } from '@angular\/core';\nimport { AuthService } from '.\/auth.service';\n\n@Component({\n  selector: 'app-login-form',\n  template: `\n    <button (click)="login()">Login<\/button>\n    <button (click)="logout()">Logout<\/button>\n  `\n})\nexport class LoginFormComponent {\n  constructor(private authService: AuthService) {}\n\n  login(): void {\n    this.authService.login();\n  }\n\n  logout(): void {\n    this.authService.logout();\n  }\n}\n<\/pre><\/div>\n\n\n
        \"\"<\/figure>\n\n\n\n
        \u05d1\u05d3\u05e8\u05da \u05d4\u05d6\u05d0\u05ea \u05db\u05dc \u05e7\u05d5\u05de\u05e4\u05d5\u05e0\u05e0\u05d8\u05d4 \u05e9\u05e6\u05e8\u05d9\u05db\u05d4 \u05d9\u05db\u05d5\u05dc\u05d4 \u05dc\u05d2\u05e9\u05ea \u05dc\u05de\u05e6\u05d1 \u05d4-login \u05e9\u05dc \u05d4\u05de\u05e9\u05ea\u05de\u05e9.<\/p>\n","protected":false},"excerpt":{"rendered":"
        The Observer Design Pattern \u05de\u05d2\u05d3\u05d9\u05e8 \u05e2\u05d1\u05d5\u05e8\u05e0\u05d5 \u05d9\u05d7\u05e1\u05d9\u05dd \u05e9\u05dc \u05d9\u05d7\u05d9\u05d3 \u05dc\u05e8\u05d1\u05d9\u05dd \u05d1\u05d9\u05df \u05d0\u05d5\u05d1\u05d9\u05d9\u05e7\u05d8\u05d9\u05dd, \u05db\u05da \u05e9\u05db\u05e9\u05de\u05ea\u05d1\u05e6\u05e2 \u05e9\u05d9\u05e0\u05d5\u05d9 \u05d1\u05d0\u05d5\u05d1\u05d9\u05d9\u05e7\u05d8 \u05e9\u05d0\u05e0\u05d7\u05e0\u05d5 \u05e2\u05d5\u05e7\u05d1\u05d9\u05dd \u05d0\u05d7\u05e8\u05d9\u05d5, \u05db\u05dc \u05d4\u05ea\u05dc\u05d5\u05d9\u05d9\u05dd \u05d1\u05d5 \u05d9\u05e7\u05d1\u05dc\u05d5 \u05d4\u05d5\u05d3\u05e2\u05d4 \u05d5\u05d9\u05ea\u05e2\u05d3\u05db\u05e0\u05d5. \u05de\u05d4 \u05d6\u05d4 Observer Design Pattern? \u05e0\u05e0\u05d9\u05d7 \u05e9\u05d9\u05e9 \u05dc\u05db\u05dd \u05e2\u05e8\u05d5\u05e5 \u05d9\u05d5\u05d8\u05d9\u05d5\u05d1. \u05d1\u05db\u05dc \u05e4\u05e2\u05dd \u05db\u05e9\u05d0\u05ea\u05dd \u05de\u05e2\u05dc\u05d9\u05dd \u05d5\u05d9\u05d3\u05d0\u05d5, \u05db\u05dc \u05d4\u05de\u05e0\u05d5\u05d9\u05d9\u05dd \u05e9\u05dc\u05db\u05dd \u05de\u05e7\u05d1\u05dc\u05d9\u05dd \u05d4\u05d5\u05d3\u05e2\u05d4. \u05d4\u05e2\u05e8\u05d5\u05e5 \u05e9\u05dc\u05db\u05dd "\u05e0\u05e6\u05e4\u05d4" \u05e2\u05dc \u05d9\u05d3\u05d9 \u05d4\u05de\u05e0\u05d5\u05d9\u05d9\u05dd \u05e9\u05d4\u05dd "\u05e6\u05d5\u05e4\u05d9\u05dd". \u05db\u05e9\u05de\u05e2\u05dc\u05d9\u05dd \u05e1\u05e8\u05d8\u05d5\u05df […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ocean_post_layout":"","ocean_both_sidebars_style":"","ocean_both_sidebars_content_width":0,"ocean_both_sidebars_sidebars_width":0,"ocean_sidebar":"","ocean_second_sidebar":"","ocean_disable_margins":"enable","ocean_add_body_class":"","ocean_shortcode_before_top_bar":"","ocean_shortcode_after_top_bar":"","ocean_shortcode_before_header":"","ocean_shortcode_after_header":"","ocean_has_shortcode":"","ocean_shortcode_after_title":"","ocean_shortcode_before_footer_widgets":"","ocean_shortcode_after_footer_widgets":"","ocean_shortcode_before_footer_bottom":"","ocean_shortcode_after_footer_bottom":"","ocean_display_top_bar":"default","ocean_display_header":"default","ocean_header_style":"","ocean_center_header_left_menu":"","ocean_custom_header_template":"","ocean_custom_logo":0,"ocean_custom_retina_logo":0,"ocean_custom_logo_max_width":0,"ocean_custom_logo_tablet_max_width":0,"ocean_custom_logo_mobile_max_width":0,"ocean_custom_logo_max_height":0,"ocean_custom_logo_tablet_max_height":0,"ocean_custom_logo_mobile_max_height":0,"ocean_header_custom_menu":"","ocean_menu_typo_font_family":"","ocean_menu_typo_font_subset":"","ocean_menu_typo_font_size":0,"ocean_menu_typo_font_size_tablet":0,"ocean_menu_typo_font_size_mobile":0,"ocean_menu_typo_font_size_unit":"px","ocean_menu_typo_font_weight":"","ocean_menu_typo_font_weight_tablet":"","ocean_menu_typo_font_weight_mobile":"","ocean_menu_typo_transform":"","ocean_menu_typo_transform_tablet":"","ocean_menu_typo_transform_mobile":"","ocean_menu_typo_line_height":0,"ocean_menu_typo_line_height_tablet":0,"ocean_menu_typo_line_height_mobile":0,"ocean_menu_typo_line_height_unit":"","ocean_menu_typo_spacing":0,"ocean_menu_typo_spacing_tablet":0,"ocean_menu_typo_spacing_mobile":0,"ocean_menu_typo_spacing_unit":"","ocean_menu_link_color":"","ocean_menu_link_color_hover":"","ocean_menu_link_color_active":"","ocean_menu_link_background":"","ocean_menu_link_hover_background":"","ocean_menu_link_active_background":"","ocean_menu_social_links_bg":"","ocean_menu_social_hover_links_bg":"","ocean_menu_social_links_color":"","ocean_menu_social_hover_links_color":"","ocean_disable_title":"default","ocean_disable_heading":"default","ocean_post_title":"","ocean_post_subheading":"","ocean_post_title_style":"","ocean_post_title_background_color":"","ocean_post_title_background":0,"ocean_post_title_bg_image_position":"","ocean_post_title_bg_image_attachment":"","ocean_post_title_bg_image_repeat":"","ocean_post_title_bg_image_size":"","ocean_post_title_height":0,"ocean_post_title_bg_overlay":0.5,"ocean_post_title_bg_overlay_color":"","ocean_disable_breadcrumbs":"default","ocean_breadcrumbs_color":"","ocean_breadcrumbs_separator_color":"","ocean_breadcrumbs_links_color":"","ocean_breadcrumbs_links_hover_color":"","ocean_display_footer_widgets":"default","ocean_display_footer_bottom":"default","ocean_custom_footer_template":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"ocean_post_oembed":"","ocean_post_self_hosted_media":"","ocean_post_video_embed":"","ocean_link_format":"","ocean_link_format_target":"self","ocean_quote_format":"","ocean_quote_format_link":"post","ocean_gallery_link_images":"on","ocean_gallery_id":[],"footnotes":""},"categories":[47],"tags":[],"class_list":["post-1502","post","type-post","status-publish","format-standard","hentry","category-design-patterns","entry"],"yoast_head":"\nThe Observer Design Pattern - Code Notebook<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/epicmarketing.co.il\/notebook\/the-observer-design-pattern\/\" \/>\n<meta property=\"og:locale\" content=\"he_IL\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"The Observer Design Pattern - Code Notebook\" \/>\n<meta property=\"og:description\" content=\"The Observer Design Pattern \u05de\u05d2\u05d3\u05d9\u05e8 \u05e2\u05d1\u05d5\u05e8\u05e0\u05d5 \u05d9\u05d7\u05e1\u05d9\u05dd \u05e9\u05dc \u05d9\u05d7\u05d9\u05d3 \u05dc\u05e8\u05d1\u05d9\u05dd \u05d1\u05d9\u05df \u05d0\u05d5\u05d1\u05d9\u05d9\u05e7\u05d8\u05d9\u05dd, \u05db\u05da \u05e9\u05db\u05e9\u05de\u05ea\u05d1\u05e6\u05e2 \u05e9\u05d9\u05e0\u05d5\u05d9 \u05d1\u05d0\u05d5\u05d1\u05d9\u05d9\u05e7\u05d8 \u05e9\u05d0\u05e0\u05d7\u05e0\u05d5 \u05e2\u05d5\u05e7\u05d1\u05d9\u05dd \u05d0\u05d7\u05e8\u05d9\u05d5, \u05db\u05dc \u05d4\u05ea\u05dc\u05d5\u05d9\u05d9\u05dd \u05d1\u05d5 \u05d9\u05e7\u05d1\u05dc\u05d5 \u05d4\u05d5\u05d3\u05e2\u05d4 \u05d5\u05d9\u05ea\u05e2\u05d3\u05db\u05e0\u05d5. \u05de\u05d4 \u05d6\u05d4 Observer Design Pattern? \u05e0\u05e0\u05d9\u05d7 \u05e9\u05d9\u05e9 \u05dc\u05db\u05dd \u05e2\u05e8\u05d5\u05e5 \u05d9\u05d5\u05d8\u05d9\u05d5\u05d1. \u05d1\u05db\u05dc \u05e4\u05e2\u05dd \u05db\u05e9\u05d0\u05ea\u05dd \u05de\u05e2\u05dc\u05d9\u05dd \u05d5\u05d9\u05d3\u05d0\u05d5, \u05db\u05dc \u05d4\u05de\u05e0\u05d5\u05d9\u05d9\u05dd \u05e9\u05dc\u05db\u05dd \u05de\u05e7\u05d1\u05dc\u05d9\u05dd \u05d4\u05d5\u05d3\u05e2\u05d4. \u05d4\u05e2\u05e8\u05d5\u05e5 \u05e9\u05dc\u05db\u05dd "\u05e0\u05e6\u05e4\u05d4" \u05e2\u05dc \u05d9\u05d3\u05d9 \u05d4\u05de\u05e0\u05d5\u05d9\u05d9\u05dd \u05e9\u05d4\u05dd "\u05e6\u05d5\u05e4\u05d9\u05dd". \u05db\u05e9\u05de\u05e2\u05dc\u05d9\u05dd \u05e1\u05e8\u05d8\u05d5\u05df […]\" \/>\n<meta property=\"og:url\" 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\u05d4\u05d5\u05d3\u05e2\u05d4 \u05d5\u05d9\u05ea\u05e2\u05d3\u05db\u05e0\u05d5. \u05de\u05d4 \u05d6\u05d4 Observer Design Pattern? \u05e0\u05e0\u05d9\u05d7 \u05e9\u05d9\u05e9 \u05dc\u05db\u05dd \u05e2\u05e8\u05d5\u05e5 \u05d9\u05d5\u05d8\u05d9\u05d5\u05d1. \u05d1\u05db\u05dc \u05e4\u05e2\u05dd \u05db\u05e9\u05d0\u05ea\u05dd \u05de\u05e2\u05dc\u05d9\u05dd \u05d5\u05d9\u05d3\u05d0\u05d5, \u05db\u05dc \u05d4\u05de\u05e0\u05d5\u05d9\u05d9\u05dd \u05e9\u05dc\u05db\u05dd \u05de\u05e7\u05d1\u05dc\u05d9\u05dd \u05d4\u05d5\u05d3\u05e2\u05d4. \u05d4\u05e2\u05e8\u05d5\u05e5 \u05e9\u05dc\u05db\u05dd "\u05e0\u05e6\u05e4\u05d4" \u05e2\u05dc \u05d9\u05d3\u05d9 \u05d4\u05de\u05e0\u05d5\u05d9\u05d9\u05dd \u05e9\u05d4\u05dd "\u05e6\u05d5\u05e4\u05d9\u05dd". \u05db\u05e9\u05de\u05e2\u05dc\u05d9\u05dd \u05e1\u05e8\u05d8\u05d5\u05df […]","og_url":"https:\/\/epicmarketing.co.il\/notebook\/the-observer-design-pattern\/","og_site_name":"Code 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