Expert refactoring guide based on Martin Fowler principles. Use when refactoring code, improving code structure, or when refactoring approach is discussed.
Refactoring (noun): A change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behavior.
Refactoring (verb): To restructure software by applying a series of refactorings without changing its observable behavior.
When refactoring, you MUST:
Based on Martin Fowler and Kent Beck's book Refactoring.
Change Function Declaration Add Parameter • Change Signature • Remove Parameter • Rename Function • Rename Method
Change Reference to Value Change Value to Reference Collapse Hierarchy Combine Functions into Class Combine Functions into Transform Consolidate Conditional Expression Decompose Conditional Encapsulate Collection Encapsulate Record Replace Record with Data Class
Encapsulate Variable Encapsulate Field • Self-Encapsulate Field
Extract Class Extract Function Extract Method
Extract Superclass Extract Variable Introduce Explaining Variable
Hide Delegate Inline Class Inline Function Inline Method
Inline Variable Inline Temp
Introduce Assertion Introduce Parameter Object Introduce Special Case Introduce Null Object
Move Field Move Function Move Method
Move Statements into Function Move Statements to Callers Parameterize Function Parameterize Method
Preserve Whole Object Pull Up Constructor Body Pull Up Field Pull Up Method Push Down Field Push Down Method Remove Dead Code Remove Flag Argument Replace Parameter with Explicit Methods
Remove Middle Man Remove Setting Method Remove Subclass Replace Subclass with Fields
Rename Field Rename Variable Replace Command with Function Replace Conditional with Polymorphism Replace Constructor with Factory Function Replace Constructor with Factory Method
Replace Control Flag with Break Remove Control Flag
Replace Derived Variable with Query Replace Error Code with Exception Replace Exception with Precheck Replace Exception with Test
Replace Function with Command Replace Method with Method Object
Replace Inline Code with Function Call Replace Loop with Pipeline Replace Magic Literal Replace Magic Number with Symbolic Constant
Replace Nested Conditional with Guard Clauses Replace Parameter with Query Replace Parameter with Method
Replace Primitive with Object Replace Data Value with Object • Replace Type Code with Class
Replace Query with Parameter Replace Subclass with Delegate Replace Superclass with Delegate Replace Inheritance with Delegation
Replace Temp with Query Replace Type Code with Subclasses Extract Subclass • Replace Type Code with State/Strategy
Return Modified Value Separate Query from Modifier Slide Statements Consolidate Duplicate Conditional Fragments
Split Loop Split Phase Split Variable Remove Assignments to Parameters • Split Temp
Substitute Algorithm
The most frequently used refactorings include:
