Notes: Refactoring -- Bad Smells in Code

 

1. Duplicated Code
1. In a class: Extract Method
2. Sibling classes:
• Extract Method -> Pull Up Method(superclass)
• Extract Method -> Form Template Method
• Substitute Algorithm
3. Extract Class

2. Long Method (Comments)
1. Extract Method
2. Replace Temp with Query
3. Introduce Parameter Object/Preserve Whole Object
4. Replace Method with Method Object
5. Decompose Conditional

3. Large Class
1. Extract Class
2. Extract Subclass
3. Extract Interface
4. Duplicate Observed Data (GUI class)

4. Long Parameter List (Dependency structure)
1. Replace Method with Method Object
2. Preserve Whole Object
3. Introduce Parameter Object

5. Divergent Change
1. Extract Class (Strategy/Visitor/Self Delegation)

6. Shotgun Surgery
1. Move Method/ Move Field
2. Inline Class

7. Feature Envy
1. Move Method
2. Extract Method -> Move Method

8. Data Clumps
1. Extract Class
2. Introduce Parameter Object/ Preserve Whole Object

9. Primitive Obsession
1. Replace Data Value with Object
2. Replace Type Code with Class/Replace Type Code with Subclass/Replace Type Code with State/Strategy
3. Extract Class
4. Introduce Parameter Object
5. Replace Array with Object

10. Switch Statements (Polymorphism)
1. Extract Method
2. Move Method
3. Replace Type Code with Subclass/Replace Type Code with State/Strategy
4. Replace Conditional with Polymorphism
5. Replace Parameter with Explicit Methods
6. Introduce Null Object

11. Parallel Inheritance Hierarchies (Shotgun Surgery)
1. Move Method
2. Move Field

12. Lazy Class
1. Collapse Hierarchy
2. Inline Class

13. Speculative Generality
1. Collapse Hierarchy (abstract class)
2. Inline Class (delegation)
3. Remove Parameter
4. Rename Method

14. Temporary Field
1. Extract Class
2. Introduce Null Object

15. Message Chains (structure of navigation)
1. Hide Delegate
2. Extract Method
3. Move Method

16. Middle Man (encapsulation/delegation)
1. Remove Middle Man
2. Inline Method
3. Replace Delegation with Inheritance

17. Inappropriate Intimacy
1. Move Method/Move Field
2. Change Bidirectional Association to Unidirectional
3. Extract Class
4. Hide Delegate
5. Replace Inheritance with Delegation

18. Alternative Classes with Different Interfaces
1. Rename Method
2. Move Method
3. Extract Superclass

19. Incomplete Library Class
1. Introduce Foreign Method
2. Introduce Local Extension

20. Data Class
1. Encapsulation Field
2. Encapsulation Collection
3. Remove Setting Method
4. Move Method
5. Extract Method
6. Hide Method

21. Refused Bequest
1. Replace Inheritance with Delegation

22. Comments
1. Extract Method
2. Rename Method
3. Introduce Assertion