Memento - Flutter

• Memento - Flutter

class TaskMemento {
  final String task;

  TaskMemento(this.task);
}

//--------------------------------


class TaskList {
  List<String> tasks = [];

  TaskMemento createBackup() {
    return TaskMemento(tasks.last);
  }

  void restore(TaskMemento memento) {
    tasks.add(memento.task);
  }

  void addTask(String task) {
    tasks.add(task);
  }

  void removeLastTask() {
    if (tasks.isNotEmpty) {
      tasks.removeLast();
    }
  }
}

//--------------------------------

class TaskHistory {
  final List<TaskMemento> history = [];

  void addMemento(TaskMemento memento) {
    history.add(memento);
  }

  TaskMemento getMemento() {
    if (history.isNotEmpty) {
      final lastIndex = history.length - 1;
      final lastMemento = history[lastIndex];
      history.removeLast();
      return lastMemento;
    }
    return null;
  }
}


//--------------------------------


void main() {
  final taskList = TaskList();
  final history = TaskHistory();

  taskList.addTask('Buy milk'); // Adding a task
  taskList.addTask('Study Flutter'); // Adding another task
  print('Current tasks: ${taskList.tasks}');

  taskList.removeLastTask(); // Removing the last task
  final removedTask = taskList.createBackup(); // Saving the removed task
  history.addMemento(removedTask); // Storing in history

  print('Tasks after removing the last one: ${taskList.tasks}');

  // Simulating undoing the task removal
  final restoredTask = history.getMemento(); // Retrieving the removed task
  if (restoredTask != null) {
    taskList.restore(restoredTask); // Restoring the task
  }

  print('Tasks after undo: ${taskList.tasks}');
}