The document discusses refactoring code to improve quality and maintainability. It provides examples of refactoring techniques like renaming variables and methods, extracting classes and interfaces, simplifying expressions, and using a null object pattern to avoid null checks. The goal of refactoring is to make code more understandable, predictable, and easier to modify while maintaining existing functionality.

1. for quality

2. X 2+3x+1==(x+1)(x+2)
 Improved code structure
 Same executable behavior

3.  Easy write, change
 Deferred complexity
 Quality
 Velocity!

4.  Understandable
 Predictable
 Changes Localized

5.  We dig design patterns
 We TDD
 Incremental

6.  Ensure working version
 Create/Ensure tests
 Use version control

7.  +:Variable, Method
 ++: Class, Class Interaction

8.  Var rename; method
rename; method extract
 Interface/class extract

9.  Safeand easy
 Limited to simple ref’

13.  Distinguish Good Design
To the point Readable Simple
Predictable/ Modifiable Testable
Uncoupled

14.  Where to refactor first?
Point Readable Simple Predictable Modify
/uncoupled
Dup code Renaming Switch Refused Parallel
Large class Long method bequest hierarchy
Lazy class Large class Feature
Speculative Envy
generality Intimacy

15.  Sharing
 Consuming

16.  Takean example of smell
and a change

17.  Demo
 Identifysmells
 Propose moves

18.  Demo
 Identify the qualities

19.  Discussion

20.  Minor: As you go
 Major: At mini-
feature/class completion
 Not as a separate milestone

21.  Quality
 Adaptability
 Velocity Impact?

22.  Refactoring projects
 Code and fix
 Performance
 Procastination

23.  Your ref’experience
 Favorite ref’ moves

24.  Hopefully, answers

25.  ???

26.  Yaniv@YanivPessach.com

27.  Before and after refactoring
 Refactoring tools menus

28. int ProcessX(int x) { return x+1; }
Ren method
int IncrementPosition(int x) {
return x+1; }
int IncrementPosition(int
Ren var
oldPos) { return oldPos+1; }

30. float Distance(float x1, float y1, float x2,
float y2) { return Math.Sqrt((x1 - x2) *
(x1 - x2) + (y1 - y2) * (y1 - y2));}
Param list to class
class FloatPoint { public float x; public
float y;}
float Distance(FloatPoint p1, FloatPoint
p2) { return Math.Sqrt((p1.x - p2.x) *
(p1.x - p2.x) + (p1.y - p2.y) * (p1.y -
p2.y)); }

31. float Distance(float x1, float y1, float x2,
float y2) { return Math.Sqrt((x1 - x2) *
Simplify subexpression
(x1 - x2) + (y1 - y2) * (y1 - y2));}
class FloatPoint { public float x; public
float y;} ….
float Distance(FloatPoint p1, FloatPoint
p2) { return Math.Sqrt(p1.DeltaX(p2) *
p1.DeltaX(p2) + Math.Sqrt(p1.Deltay(p2)
* p1.DeltaY(p2)); }

33. class ShapePainter {
public void Paint(int scale); }
class AreaRenderer {
public void Render(int multiplier); }
class DrawController {
void DrawObject(object o) {
if (o is ShapePainter)
((ShapePainter)(o)).Paint(1); } }

34. Extract interface
interface IShapePainter {
void Paint(int scale); }
class ShapePainter : IShapePainter {
public void Paint(int scale); }
class AreaRenderer : IShapePainter{
Use iface
public void Paint(int multiplier); }
ren
Use iface
void DrawObject(IShapePainter o) {
o.Paint(1); }

35. class ShapePainter {
public void Paint(int scale); }
class AreaRenderer {
Extract interface
public void Render(int multiplier); }
class DrawController {
void DrawObject(object o) {
if (o is ShapePainter)
((ShapePainter)(o)).Paint(1); } }

37. class TaxCalculator { float rate;
public float GetTax(float income,
Deductions deductions) { return
(income - deductions) * rate; } }
class PayRoll { TaxCalculator tax;
Deductions deduct; float income;
float IssueCheck() { if (tax != null)
 return tax.GetTax(income, deduct);
 Else return income; } }

38. class NullTaxCalculator : TaxCalculator{
public float GetTax(float income,
Deductions deductions) { return 0; } }
class PayRoll2 { TaxCalculator tax;
Null object
Deductions deduct; float income;
float IssueCheck() { return
tax.GetTax(income, deduct); } }