natural course of refactoring - mix-it lyon 2014
DESCRIPTION
Doing refactoring seems to be obvious practice in a software development. In many teams times it is not being done at all. "We have no time to do it!". "We are not allowed". "We don't know where to start and how to do it pragmatically". Many programmers are familiar with classic refactorings or even more complex refactorings to patterns, clean code rules and naming rules. But it is not enough. Pragmatic refactoring is a difficult practice that requires many years of experience. And what if you or folks from your team don't have that experience? Then refactoring may be more harmful than useful. The Natural Course of Refactoring is a process, workflow that expresses something what may seem obvious for experienced refactoring practitioner but very difficult to figure out for beginners or even more advanced practitioners. It is like red-green-refactor for TDD. NCR is a way of thinking which shifts your focus from single refactorings to a more holistic approach. It is also decision framework helping you to specify what is next pragmatic step (if there is any).It helps you to recognize what stage the particular fragment of source code is, what you can do about it and decide if to do something or leave it as it is. It guides you what exact refactorings you should take into consideration in the particular stage and also which refactorings are way too big steps.TRANSCRIPT
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Natural Course of Refactoring. A refactoring workflow.
Mariusz Sieraczkiewicz
@ms_bnsit_pl
http://msieraczkiewicz.blogspot.com
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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.
Why refactoring is like sex?
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(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.
Why refactoring is like sex?
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(adapted from http://www.thealmightyguru.com/Humor/Docs/ProgrammingIsLikeSex.html)
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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.
Why refactoring is like sex?
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(adapted from http://www.thealmightyguru.com/Humor/Docs/ProgrammingIsLikeSex.html)
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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.
Why refactoring is like sex?
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(adapted from http://www.thealmightyguru.com/Humor/Docs/ProgrammingIsLikeSex.html)
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Code readability Natural Course of Refactoring
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.so!changesIntroDuCinG!maYBe,softwaRe,TosO,calLEdprOgRessIve,and.however.cHanGes!Modifies.usuallY,sTRucTureOFmaYbe,hoWEVeRtHecoDE,And!wHaTmaYbecumulatEdhowevEr.anD,mAkes.AnD,,and,the.LeSs!rEAdAblE,aNd.cOdeMAybe.ANd,!and,!Thenumber!of,sO,HoWEvErsodepeNdeNCiES,And.MAybeintErACtIOns!betWeenHoWevEr!differEntsyStem.moDules!inCreasESoThat,iTsO!morE.is.diffiCuLt,To,AnDuNdErstandmodIFy
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 Natural Course 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
Everyday refactoring
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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
Strategic refactoring
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When should I do strategic refactoring? Natural Course of 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
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Confront with: • team opinions
• business strategy
Frequency of changes
Complexity
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Natural Course of Refactoring The process
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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
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Everyday refactoring
Strategic refactoring
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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
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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
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