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.

Why refactoring is like sex?

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 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


Confront with: • team opinions

• business strategy

Frequency of changes

Complexity

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Natural Course of Refactoring 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


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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


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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