What is Refactoring? - Explanation & Meaning
Learn what refactoring is, how to improve code without changing behavior, and when to refactor following Martin Fowler's principles.
Definition
Refactoring is the process of restructuring existing code without changing its external behavior. The goal is to improve internal structure, readability, and maintainability while keeping functionality exactly the same.
Technical explanation
Martin Fowler defined refactoring as a disciplined technique for restructuring code in small, verifiable steps. Common refactoring techniques include: Extract Method (moving part of a function to a new function), Rename Variable (giving more meaningful names), Move Method (moving a method to a more appropriate class), Replace Conditional with Polymorphism (replacing switch statements with inheritance), and Introduce Parameter Object (bundling related parameters into an object). Code smells are indicators that refactoring is needed: long methods, large classes, duplicated code, feature envy, and shotgun surgery. The safety of refactoring depends on good test coverage: without tests, you cannot verify that behavior remains unchanged. IDE support automates many refactoring steps with guaranteed correctness. Continuous refactoring as part of daily development work is more effective than large, risky refactoring projects. The Strangler Fig pattern enables gradually replacing legacy systems.
How MG Software applies this
At MG Software, refactoring is an integral part of our development process. We apply the Boy Scout Rule and continuously refactor small improvements. Before building new features, we assess whether the existing code provides a solid foundation. We plan major refactoring efforts in consultation with clients when technical debt threatens velocity. We rely on comprehensive tests to execute refactoring safely.
Practical examples
- A team splitting a 500-line function into ten small, well-named functions, making a bug that went unnoticed for months immediately visible.
- A developer consolidating repeated code in five controllers into a shared service, so future changes are made in one place instead of five.
- An organization applying the Strangler Fig pattern to replace a monolithic legacy system module by module with microservices without a Big Bang migration.
Related terms
Frequently asked questions
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