2_observer_pattern_with_dynamic_messages.swift

protocol Logger {
  func takeAction(flag: Bool) -> Void
}

class LoggerA: Logger {
  func takeAction(flag: Bool) {
    print("LoggerA always prints this message.")
  }
}

class LoggerB: Logger {
  func takeAction(flag: Bool) {
    if flag {
      print("LoggerB, the flag is true!")
    } else {
      print("LoggerB, the flag is false!")
    }
  }
}

class FakeServer {

  var loggerList: [Logger] = [LoggerA(), LoggerB()]

  func run() {
    someImportantAction()
    notifyLoggers(flag: true)
    anotherImportantAction()
    notifyLoggers(flag: false)
  }

  private func someImportantAction() -> Void {
    print("This is some important action!")
  }

  private func anotherImportantAction() -> Void {
    print("This is another important action!")
  }

  private func notifyLoggers(flag: Bool) {
    for item in loggerList {
      item.takeAction(flag: flag)
    }
  }

}

var server = FakeServer()
server.run();