history_state_notifier 0.0.6+1

Extends state_notifier to add a history feature that allows for undo/redo operations.

DISCONTINUED

Development of this package has been discontinued due to the sunsetting of state_notifier in riverpod. If you are looking for a similar package, please check out value_notifier_tools which works with ValueNotifier instead, has no external dependencies and will be maintained actively.

Thank you for your support!

Old README:

This package offers an extension on state_notifier to add a full history support with undo/redo functionality.

Features

• ↩️ Add undo() and redo() to StateNotifier
• 🕐 Limit the size of your history
• 💕 Offers both a mixin that can be added to your existing StateNotifiers and an abstract class that you can extend
• 🪶 No dependencies on flutter or any other packages and super lightweight.
• 🔎 Choose which states get stored to the history
• 🔄 Transform states before applying them from the history

Getting started

This package is designed to work with/like StateNotifier. If you're not using StateNotifier and don't plan to use it you won't get much value out of this.

Usage

Upgrade an existing StateNotifier

class CounterNotifier extends StateNotifier<int>
    with HistoryStateNotifierMixin<int> {
  CounterNotifier() : super(0) {
    // If you want the initial state to be added to the history, do it like this
    state = 0;
    
    // This is how you limit the size of your history.
    // Set it to null to keep all state (default)
    maxHistoryLength = 30;
  }

  void increment() => ++state;

  void decrement() => --state;

  // By using temporaryState setter, the change won't be stored in history
  void reset() => temporaryState = 0;

  // You can override this function to apply a transformation to a state
  // from the history before it gets applied.
  @override
  int transformHistoryState(int newState, int currentState) {
    return newState;
  }
}

Create a HistoryStateNotifier

If you prefer to create a HistoryStateNotifier directly, you can do this instead:

class CounterNotifier extends HistoryStateNotifier<int> {
  // ... Same as above
}

Use It!

You can now use the full functionality of the HistoryStateNotifier!

// Obtain a reference however you wish
final CounterNotifier notifier = watch(counterProvider.notifier);

notifier.increment(); // 1
notifier.undo(); // 0
notifier.redo(); // 1

notifier.decrement(); // 0
notifier.undo(); // 1
notifier.canRedo // true
notifier.increment // 2
notifier.canRedo // false

// ...