Polymorphism Using Interfaces in Object Oriented Programming in Dart

void main() {
  Log myLog = new Log();
  FileLogger myFile = new FileLogger();
  ConsoleLogger myConsole = new ConsoleLogger();

  myLog.registerLogger(myFile);
  myLog.registerLogger(myConsole);

  myLog.log("Hello World!!");
  myLog.log("Second log event!");
}

class ILogger {
  void handleEvent(String event) {}
}

class FileLogger implements ILogger {
  void handleEvent(String event) {
    print(event);
  }
}

class ConsoleLogger implements ILogger {
  void handleEvent(String event) {
    print(event);
  }
}

class Log {
  List listeners = [];

  void registerLogger(ILogger logger) {
    listeners.add(logger);
  }

  void log(String event) {
    for (ILogger logger in listeners) {
      logger.handleEvent(event);
    }
  }
}
  

Output

Hello World!!
Hello World!!
Second log event!
Second log event!