No Undo/Redo History

Description

What does it look like?

• User actions are not recorded, so undo/redo functionality is unavailable
• There is no way to revert the side effects of an operation
• Without a history, it is difficult to restore or roll back system state

Why is it a problem?

• Poor user experience (UX) — no way to undo mistakes
• Recovery from input errors requires redoing or restoring manually
• Difficult to debug or trace issues in complex state changes

Bad Example of the Anti-pattern

TypeScript

class TextEditor {
  private content: string = "";

  type(text: string) {
    this.content += text;
  }

  getContent() {
    return this.content;
  }
}

const editor = new TextEditor();
editor.type("Hello ");
editor.type("World");

console.log(editor.getContent()); // Hello World

// 取り消しができない！

PHP

<?php

class TextEditor {
  private string $content = "";

  public function type(string $text): void {
    $this->content .= $text;
  }

  public function getContent(): string {
    return $this->content;
  }
}

// 利用例
$editor = new TextEditor();
$editor->type("Hello ");
$editor->type("World");

echo $editor->getContent(); // Hello World

// 取り消しができない！

Python

class TextEditor:
    def __init__(self):
        self.content = ""

    def type(self, text: str):
        self.content += text

    def get_content(self) -> str:
        return self.content

# 利用例
editor = TextEditor()
editor.type("Hello ")
editor.type("World")

print(editor.get_content())  # Hello World

# 取り消しができない！

Issues:

• Input is applied directly to the internal state — no way to undo
• type() modifies the content immediately, making history management difficult

Refactoring by Pattern

Design patterns that can address this

Pattern	Overview	Main Refactoring Approach
Command	Encapsulate operations as command objects and manage execute/undo/redo	Store and control execution history
Memento	Capture and restore full snapshots of an object’s state	Enable complete state restoration