Mutable data

코드 악취 중 하나.

관련 리팩토링

• Encapsulate variable
• Split variable
• Slide statements
• Extract function
• Separate query from modifier
• Remove setting method
• Replace derived variable with query
• Combine functions into class
• Combine functions into transform
• Change reference to value

함수형 프로그래밍

변하는 데이터 그 자체를 문제의 원인으로 보는 접근:

For this reason, an entire school of software development—functional programming—is based on the notion that data should never change and that updating a data structure should always return a new copy of the structure with the change, leaving the old data pristine. —Chapter 3, Refactoring: Improving the design of existing code

(모든 함수형 프로그래밍이 변수를 허용하지 않는 건 아니다.)