🧪️ Need to Implement Undo/Redo

✅ Problem Overview

In applications such as forms, editors, or GUIs, users often expect "Undo" and "Redo" functionality.
However, implementing these features ad hoc can lead to scattered logic, manual state tracking, and brittle code.

Common challenges include:

• No centralized history of operations
• Asymmetrical or inconsistent undo/redo behavior
• Mixed responsibilities between actions and state transitions, making the code hard to test and extend

✅ Solution Overview

Use the Command pattern to represent operations as objects and
use the Memento pattern to take snapshots of the system's state for recovery.

Concern	Applied Pattern
Capturing and managing actions	Command
Saving and restoring state	Memento

By separating "what happened" from "what changed", the system can maintain a clear and consistent undo/redo mechanism.

✅ Pattern Synergy

Role	Example Implementation
Executable/undoable action	EditCommand, InsertCommand
Captured state	EditorMemento
State owner	Editor (Originator of Memento)
Command and history manager	HistoryManager (Invoker)

Each command triggers a Memento snapshot before modifying the state.
The HistoryManager tracks both the actions and the corresponding states to perform undo/redo operations.

✅ UML Class Diagram

✅ Explanation

This structure separates action execution from state management:

• Each operation is encapsulated as a Command object (EditCommand)
• The state is saved before the command executes via Memento (EditorMemento)
• HistoryManager stores both commands and mementos for history control

This architecture enables:

• Self-contained undo/redo behavior per command
• Decoupled logic between state and execution
• Centralized, testable history tracking

✅ Practical Notes

• ✅ Well-suited for editors, drawing apps, and any input-driven interface with revertibility
• ✅ Also applicable for transaction control, multi-step form navigation, or timeline-based editing
• ✅ Command and Memento decouple responsibilities, simplifying testing and rollback logic

✅ Summary

• Use Command to encapsulate operations and store execution history
• Use Memento to snapshot and restore application state
• Together, they provide a structured and reliable way to implement undo/redo
• Enhances UX and developer confidence through clear, reversible logic

This design ensures flexibility and robustness in scenarios where precise user operation tracking and recovery are required.