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Refactoring Dhaval Dalal software-artisan.com @softwareartisan
| Date post: | 09-May-2015 |
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John Thompson, the hatter makes and sells hats for ready money!
Refactoring Metaphor
John Thompson, the hatter makes and sells hats for ready money!
Refactoring Metaphor
John Thompson, the hatter makes and sells hats for ready money!
Refactoring Metaphor
John Thompson, the hatter makes and sells hats for ready money!
Refactoring Metaphor
What is Refactoring?
Refactoring means improving the design after it has been written.
Martin Fowler.
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.
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Why Should I Refactor?
Martin Fowler.
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.
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.
Code Smells…lets code along! Duplicate Code
! Switch Statements
! Long Method
! Long Parameter List
! Large Class
! Speculative Generality Kent Beck
If it Stinks, Change it!
! Indecent Exposure
! Divergent Change
! Shotgun Surgery
! ...and many more.
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
Stronger Deodorizing Agents…! Replace Array with Object
! Replace conditionals with Polymorphism
! Replace Type Code with State/Strategy
! Introduce Null Object ...and many more
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.
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Refactoring Cycle
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Choose on appropriate
Refactoring to applyApply Refactoring
Run ALL Tests (Get GREEN Bar)
Reached Desired
Structure?
Yes
No
Undertaking Big Refactorings (Bridge Replacement Metaphor)! Let traffic continue to
flow on old bridge.
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! Create new refactored implementation.
! 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.
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.
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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.
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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
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When to Refactor?
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.
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No Silver Bullet
Martin Fowler
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.
References! Refactoring
" Martin Fowler.
! Refactoring to Patterns " Joshua Kerievsky.
! Refactoring Motivations " Jay Fields’ Blog
! Creating an Agile Culture to drive organizational Change " David Anderson
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