Natural course of refactoring - Mix-IT Lyon 2014

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Natural Course of Refactoring.
A refactoring workflow.
Mariusz Sieraczkiewicz
@ms_bnsit_pl
http://msieraczkiewicz.blogspot.com
1

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Why refactoring is like sex?
Natural Course of Refactoring

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Once you get started, you’ll only stop
because you’re exhausted.
One mistake and the consequences
may be really huge.
Natural Course of Refactoring 2014 3
(adapted from http://www.thealmightyguru.com/Humor/Docs/ProgrammingIsLikeSex.html)

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People more talk about it than
actually do.
You can do it for money or for fun.
It’s not really an appropriate topic for
dinner conversation.

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Beginners do a lot of noise about it.
Some people are just naturally good at it,
.. but some people will never realize how
bad they are, and you’re wasting your time
trying to tell them.

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It doesn’t go so well when you’re
drunk, but you’re more likely to do it.
You’ll miss it after a longer break.

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Code readability

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.so!changesIntroDuCinG!maYBe,softwaRe,TosO,
calLEdprOgRessIve,and.however.cHanGes!Modi
fies.usuallY,sTRucTureOFmaYbe,hoWEVeRtHeco
DE,And!wHaTmaYbecumulatEdhowevEr.anD,m
Akes.AnD,,and,the.LeSs!rEAdAblE,aNd.cOdeMA
ybe.ANd,!and,!Thenumber!of,sO,HoWEvErsode
peNdeNCiES,And.MAybeintErACtIOns!betWeen
HoWevEr!differEntsyStem.moDules!inCreasESo
That,iTsO!morE.is.diffiCuLt,To,AnDuNdErstandm
odIFy
Why is it difficult to understand software after some
time of its evolution?

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Introducing changes to software (so called
progressive changes) usually modifies
structure of the code, what cumulated
makes the code less readable. The number
of dependencies and interactions between
different system modules increase, so that
it is more difficult to understand and
modify.
Why is it difficult to understand software after some
time of its evolution?

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Even answers to easy questions are difficult to
find.
The problem lies more in a code readibility,
than in the programmers reading skills.
Even great reader will not perform good in
such environment.
What alters programmers productivity in this case?

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Flavours of refactoring

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Two flavours of refactoring

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Everyday refactoring
Within a reach of every programmer
Can be done in minutes
Mostly safe, IDE-base automatic refactorings
For local health of the code
Part of programming practice
No excuse for not doing it
Main practices
Cleaning names
Naming conditions
Extracting methods
Moving methods and extracting classes

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Strategic refactoring
A team longer term effort
Requires aligning with iteration planning
Generates items in backlog
Risky activity that requires intensive testing (including good
tests suite)
Difficult and time-consuming
Check carefully if refactoring gives you enough value
(Feather’s Quadrant)
Main practices
Introducing high level design patterns
Introducing architectural changes

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When should I do strategic refactoring?

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1. complexity := 1
2. For every decision point (if, while, for,
and, or, try, case, break, continue)
complexity++
3. if 6 <= complexity <= 10 – simplify a
method
4. if complexity > 10 – compose method
McCabe Metric (Cyclomatic Complexity)
Simplified version

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High complexity/
Seldom changes
Don’t touch it.
High complexity/
Frequent changes
Apply strategic
refactoring
Low complexity/
Seldom changes
Utils, good for
experiments
Low
complexity/Frequent
changes
Heaven 
Feather’s Quadrant
Confront with:
• team opinions
• business strategy
Frequency of changes
Complexity

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The process

www.bnsit.pl Natural Course of Refactoring 2014 19

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Step 0. Understand the code

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Sometimes it is the most difficult point
Try to…
• find an author and ask for help
• find somebody who worked with the code and
ask for help
• find somebody who knows the system (or
module) and ask for help
• Do it yourself if none of above are possible
Understand

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Mental tools
Simple code cleaning
Clean up the names
Add temporary comments to the code
Introduce lazy variables initialization
Make optical cleanup (make more space)
Scaffolding refactoring
Do some exploratory refactoring to be thrown away
The only goal is to gain more understanding of the code
Done in Notepad or something similar
Understand

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They should be temporary. Delete them after refactoring.
// SMELL it doesn’t look good, copy-
paste antipattern
// REFACTOR introduce factory
// NOTE send a message
// IDEA it can be modeled as a state
machine
Introduce refactoring comments

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Step 1. Express algorithm

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Aim
Code that speaks to you
Mental tools
• Compose method
• Introduce Method Object Refactoring
• Extract method
Express algorithm

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Step 2. Extract responsibilities

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Move meaningful private methods to another
classes.
You can’t test private method without hacks so
if it is worth testing, find another class where
this method will be public.
Extract responsibilities

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Mental tools
Single responsibility principle
Move method refactoring
Extract class refactoring
Introduce Domain Object
Introduce Value Object
Extract responsibilities

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Step 3. Introduce flexibility

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Flexibility based on requirements
eg. be prepared for many cripting algorithms, starting with 5
Flexibility which emerged from code
eg. your team has written 8 reports with similar structure
Never guess for flexibility
Do you REALLY need flexibility?

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Strategy, Template method – different versions
of the same algorithm
State – simple state machines
Factory – polimorphic object creation
Builder – creating complex object in multiple
steps
Decorator – flexibility in enhancing behaviour
at runtime
Observer – loosen dependencies by indirect
communication (events)
Some design patterns applications

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Mental tools
S.O.L.I.D.
Design patterns
Refactoring to patterns
Apply design patterns

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Step 4. Evolve architecture

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It is always a strategic decision.
It is useful to have regular Design Retrospective
meetings when such ideas are discussed.
Evolve architecture

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Mental tools
Introducing/removing layers
Introducing or replacing ORM/NoSQL/?
Important change in building blocks
Changing or introducing new framework
Introducing events
Introducing state machine
Moving towords DDD, Microservices, CQRS
Introducing Bounded-Context (DDD)
Applying Anticorruption Layer
Evolve architecture

www.bnsit.pl Natural Course of Refactoring 2014 37

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It is just a model – neither true nor false
Big classes and big methods has fragments of code
in different NCR stages
Quite seldom code is in Compose method step
(which the most increases readability)
The consecutive steps are done more seldom than
preceding ones
Some comments

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Extracting responsibilities and Introducing
flexibility should be attracted by current
architecture vision (Architectural Mantra)
Lack of the architecture vision may push you to
local optimum
NCR is an ongoing process and should be a part
of whole software process.
NCR and architecture
Techniki pracy z kodem

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Why NCR?
Easy to teach
Easy to understand and remeber
Separates everyday and strategic refactoring
Indicates the simplest (safe) possible step in the
moment
Gives hints what kind of refactorings can be
applied in the moment
NCR IN A TEAM

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Natural Course of Refactoring.
A refactoring workflow.
Mariusz Sieraczkiewicz
@ms_bnsit_pl
http://msieraczkiewicz.blogspot.com
41

Natural course of refactoring - Mix-IT Lyon 2014

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