1. Refactoring
Dhaval Dalal
software-artisan.com
@softwareartisan

2. dhaval.dalal@software-artisan.com
Refactoring Metaphor
John Thompson, the hatter makes
and sells hats for ready money!

3. dhaval.dalal@software-artisan.com
Refactoring Metaphor
John Thompson, the hatter makes
and sells hats for ready money!

4. dhaval.dalal@software-artisan.com
Refactoring Metaphor
John Thompson, the hatter makes
and sells hats for ready money!

5. dhaval.dalal@software-artisan.com
Refactoring Metaphor
John Thompson, the hatter makes
and sells hats for ready money!

6. dhaval.dalal@software-artisan.com
Refactoring Metaphor
John Thompson

7. dhaval.dalal@software-artisan.com
What is Refactoring?
Refactoring means improving the design
after it has been written.
Martin Fowler.

8. dhaval.dalal@software-artisan.com
Why Should I Refactor?
! Development is a process of Discovery
and code constantly evolves.
! Refactoring is a code curative
technique, just as Sleep is a Curative
Agency for the body playing part in
repairing mechanism of the body.
5

9. dhaval.dalal@software-artisan.com
Why Should I Refactor?
Any fool can write code that a computer
can understand. Good programmers write
code that humans can understand. The
purpose of refactoring is to make the
software easier to understand and modify.
Martin Fowler.

10. dhaval.dalal@software-artisan.com
Why Should I Refactor?
! It improves the design of software
" By repairing a highly coupled, non-cohesive
design.
! Helps to find bugs faster.
! Helps to Program Faster.

11. dhaval.dalal@software-artisan.com
Code Smells…lets code along
! Duplicate Code
! Switch Statements
! Long Method
! Long Parameter List
! Large Class
! Indecent Exposure
! Divergent Change
! Shotgun Surgery
! ...and many more.
If it Stinks,
Change it!
! Speculative Generality Kent Beck

12. dhaval.dalal@software-artisan.com
Deodorize With Fresheners…code along
! Encapsulate Collections
! Encapsulate Downcast
! Replace Error Code with Exception
! Introduce Variable
! Introduce Symbolic Constants
! Rename Method/Variable
! Remove Control Flag
! Simplify Conditionals
! Simply Nested Conditionals with Guard Clauses
! Move Method
! Chain Multiple Constructors/Methods
! Replace Type Code with Enums or Class

13. dhaval.dalal@software-artisan.com
Stronger Deodorizing Agents…
! Replace Array with Object
! Replace conditionals with Polymorphism
! Replace Type Code with State/Strategy
! Introduce Null Object
...and many more

14. dhaval.dalal@software-artisan.com
General Principles in Refactoring
! From Near to Far.
" That which is obvious and close to us now
is the starting point, a.k.a the inflection
point.
" That which is abstract is the goal.
! Take baby-steps.
11

15. dhaval.dalal@software-artisan.com
Refactoring Cycle
12
Choose on
appropriate
Refactoring to apply
Apply Refactoring
Run ALL Tests
(Get GREEN Bar)
Reached
Desired
Structure?
Yes
No

16. dhaval.dalal@software-artisan.com
Undertaking Big Refactorings
(Bridge Replacement Metaphor)
! Let traffic continue to
flow on old bridge.
! Create new refactored
implementation.
13
! Create another bridge
side-by-side the old one.
! Take an Interface-oriented
approach.
! House the old code in
one implementation.
! When the new bridge is
ready, delink traffic from
the old one and re-route it
over the new bridge.
! Use the new impl. by
replacing the old one.

17. dhaval.dalal@software-artisan.com
Refactoring To Patterns
! Arrive to pattern via series of small
refactorings.
" Rigorously apply OO principles along-side
continuous refactoring.
# SRP, OCP, LSP, ISP, DIP (SOLID) etc...
" You will eventually evolve to some known
pattern.
! When you “intuit” that a pattern will
readily apply.
" Approach this in baby steps. 14

18. dhaval.dalal@software-artisan.com
Refactoring and Legacy Code
! Code without tests is Legacy.
" Does anyone still create this?
" Michael Feathers’ has an excellent book on
this.
#Working Effectively with Legacy Code
! Refactoring code without tests is like
performing a tight-rope walk without any
safety net underneath.
15

19. dhaval.dalal@software-artisan.com
Motivators and Inhibitors

20. dhaval.dalal@software-artisan.com
As in many things the answer lies in
balancing opposing forces,
especially when its difficult to make
hidden Business Value explicit.
Pragmatic Vs Dogmatic
Agility Vs Fragility
17
When to Refactor?

21. dhaval.dalal@software-artisan.com Views on Refactoring
! A traditionalist view on Refactoring is
re-work!
! In reality, it is responding to new
information as it arrives.
! At the same time, avoid “Major
Refactorings”
" Do initial architecture envisioning.
18

22. dhaval.dalal@software-artisan.com
No Silver Bullet
Refactoring is no “silver bullet”, yet it is
a valuable tool, a pair of silver pliers
that helps you keep good grip on your
code. Without refactoring, the design
of the program will decay.
Martin Fowler

23. dhaval.dalal@software-artisan.com
References
! Refactoring
" Martin Fowler.
! Refactoring to Patterns
" Joshua Kerievsky.
! Refactoring Motivations
" Jay Fields’ Blog
! Creating an Agile Culture to drive organizational Change
" David Anderson

24. Thank You!
Dhaval Dalal
dhaval.dalal@software-artisan.com