refactoring

Note and code sample for reading Refactoring - Improving the design of existing code

The code might not be executed, the main purpose is to interpret the theory of refactoring

Principles in Refactoring

Bad Smells in Code

Building Tests

Toward a Catalog of Refactorings

Composing Methods

• Extract Method
• Inline Method
• Inline Temp
• Replace Temp with Query
• Introducing Explaining Variable
• Split Temporary Variable
• Remove Assignments to Parameters
• Replace Method with Method objects
• Substitute Algorithm

Moving Features Between Objects

• Move Method
• Move Field
• Extract Class
• Inline Class
• Hide Delegate
• Remove Middle Man
• Introduce Foreign Method
• Introduce Local Extension

Organizing Data

• Self Encapsulate Field
• Replace Data Value with Object
• Change Value to Reference
• Change Reference to Value
• Replace Array with Object
• Duplicate Observed Data
• Change Unidirectional Association to Bidirectional
• Change Bidirectional Association to Unidirectional
• Replace Magic Number with Symbolic Constant
• Encapsulate Field
• Encapsulate Collection
• Replace Record with Data Class
• Replace Type Code with Class
• Replace Type Code with subclass
• Replace Type Code with State/Strategy
• Replace Subclass with Fields

Simplifying Conditional Expressions

• Decompose Conditional
• Consolidate Conditional Expression
• Consolidate Duplicate Conditional Fragments
• Remove Control Flag
• Replace Nested Conditional with Guard Clauses
• Replace Conditional with Polymorphism
• Introduce Null Object
• Introduce Assertion

Making Method Calls Simpler

• Rename Method
• Add Parameter
• Remove Parameter
• Separate Query from Modifier
• ParameterizeMethod
• ReplaceParameterWithExplicitMethods
• Preserve Whole Object
• Replace Parameter with Method
• Introduce Parameter Object
• Remove Setting Method
• Hide Method
• Replace Constructor with Factory Method
• Encapsulate Downcast
• Replace Error Code with Exception
• Replace Exception with Test

Dealing with Generalization

• Pull Up Field
• Pull Up Method
• Pull Up Constructor Body
• Push Down Method
• Push Down Field
• Extract Subclass
• Extract Superclass
• Extract Interface
• Collapse Hierarchy
• Form Template Method
• Replace Inheritance with Delegation
• Replace Delegation with Inheritance

Big Refactorings

• Tease Apart Inheritance
• Convert Procedural Design to Objects
• Separate Domain from Presentation
• Extract Hierarchy

Putting it All Together