clean code

1. Steve Rodgers
steve.rodgers@gmail.com
CODE QUALITY

2. AN APOLOGY

3. THE DREAM
Metronomic build/fix/deploy cycle
Bug count always low per release
End users love the app as it never crashes 
Stakeholder 
QA 
Support team 
Project Manager 
Devs 
Imagine a world where

4. WHY CARE PART 1?
Business *MUST* care

5. WHY CARE PART 2
Developers *SHOULD* care

6. WHY CARE PART 3
The Quality Trade Off

7. THE MISSION: BUILD A MAINTAINABLE
LEGACY
Code spends most of its life being maintained
How hard is it to learn any new code base?
What is your legacy?
My $hit code will be your problem tomorrow
Your $hit code will be my problem today

8. MALLEABLE CODE
Code is rarely done unless it’s demo code
Business requirements change all the time
Code must therefore be engineered to handle continual
refactor
Code must be thought of as highly malleable
Every line is always up for possible refactor
How will you survive dominate in this world?
In The Real World

9. TIP: WRITE UNIT TESTS
Why write tests?
Validate class behaviour now and future proof it
Domain classes with behaviour must have tests
Data classes don’t need tests
Write meaningful tests
Be highly suspicious of 100% unit test coverage 
Be judicious; spend money where needed
Write tons of tests for critical algorithm
Don’t write tons of tests for 3 line method
Learn TDD then Practice TDD

10. TIP: AVOID WRITING GOD CLASSES
“A ‘God Class’ is an object that controls way too many
other objects in the system and has grown beyond all logic
to become The Class That Does Everything.”
[http://c2.com/cgi/wiki?GodClass]
The signs
1200 SLOC? 50 private methods? 35 fields?
No one in the team understands how it works?
The disease

11. GOD CLASS: UNIT TESTS HARD TO WRITE?
Class is hard to test?
Lots of complicated test setup code?
Lots of Asserts per test?
A unit test should only have a single Assert
Unit test on Elm Street

12. TIP: ADOPT SINGLE RESPONSIBILITY
PRINCIPLE
Class should have one responsibility
Refactor God class into multiple SRP classes
Write unit tests for each SRP class
The cure

13. TIP: AVOID UNMANAGED COMPLEXITY
Signals: Many lines of code, tons of methods but few
classes
Avoid function decomposition
Private method syndrome
Private methods cannot be unit tested
Embrace class decomposition
Lots of little classes
Write battery of unit tests for each little class
Refactor big private methods out into their own class (see
‘method-object’ Kent Beck)

14. TIP: USE SOFTWARE DESIGN PATTERNS
Don’t miss out on GOF patterns
Factory, Null Object, Decorator, Adapter etc
Patterns signal intent to other developers
Use only when needed
Don’t force them in when not needed
Be suspicious of large code base that doesn’t use patterns

Beware Dunning-Kruger Effect

15. CYCLOMATIC COMPLEXITY
“Cyclomatic complexity is a software metric
(measurement), used to indicate the complexity of a
program. It is a quantitative measure of the number of
linearly independent paths through a program's source
code.”
[https://en.wikipedia.org/wiki/Cyclomatic_complexity]

16. TIP: REDUCE HEAVY USE OF IMPERATIVE
STYLE
Complicated code is hard to understand
Nested if/else with lots of || and &&
Cyclomatic complexity is the work of the devil
Reduce use of imperative programming style
e.g. if/else/switch
Flock of seagulls lead to the gates to Hades {{{}}}
Challenge each other to reduce heavy use of them
Good use of OO, LINQ & patterns will help achieve this goal
Favour a functional programming style
e.g. LINQ
But avoid nested lambda hell

17. TIP: PUBLISH CYCLOMATIC COMPLEXITY
Dashboards like Sonar publish cyclomatic complexity
during the build for all to see
Visual Studio “Code Metrics” gives cyclomatic complexity
drill down
ReSharper add-on can graphically show cyclomatic
complexity in Visual Studio

18. CYCLOMATIC COMPLEXITY DEMO

19. TIP: AVOID STATIC
Static references & classes defeat unit testing
E.g. How do you mock DateTime.Now for daylight savings
unit tests when they run on January 14th?
Wrap use of static classes in an injected singleton that
delegates to static implementation
E.g. Define and implement IDateTime interface
Avoid ‘XyzHelper’ or ‘Util’ classes like the plague!

20. TIP: USE AWESOME NAMES EVERYWHERE
Take time to name every artefact
Class, method, field, property, parameter, automatic variable (prod
code + test code)
Class name is a noun
Method name is a verb
E.g. dog.Sleep(), table.Clear(),
documentAggregator.Aggregate()
Stuck for class name? http://classnamer.com 
E.g.
for(int p = 0; p < 10; p++) {}
for(int personIndex = 0; personIndex < 10;
personIndex++) {}

21. TIP: WRITE CLEAN CODE
Broken Window Theory
“maintaining and monitoring urban environments to preve
nt small crimes such as vandalism, public drinking and toll
-
jumping helps to create an atmosphere of order and lawful
ness, thereby preventing more serious crimes from
happening”
Corollary: Keep code+tests uber clean
[https://en.wikipedia.org/wiki/Broken_windows_theory]
Uncle Bob says ‘Keep it clean!’

22. TIP: AVOID INHERITANCE
Default to avoid inheritance: ‘is-a’
Why? Derived often needs to know base intimately
Default to favour composition: ‘has-a’
Only cave-in when ‘is-a’ rule satisfied
Dog is-a bone: fail
Dog has-a bone: pass
Cat is-a mammal: pass
Cat has-a mammal: fail

23. TIP: CODE REVIEW BEFORE CHECK-IN
Ideally every check-in gets peer reviewed prior to
check-in
Each check-in should have:
Description + name of reviewer
Over the shoulder review preferential
Rotate reviewers and share knowledge and tips within the
team == free peer training; level up
Also back up with post commit code review tool e.g.
Crucible

24. TIP: HOW TO CONDUCT CODE REVIEW
1. Park egos at the door
2. Team first attitude
3. Test coverage good?
4. Lots of private methods? God class?
5. Inheritance satisfies ‘is-a’ rule?
6. Interface based programming? Use of ‘new’ operator?
7. Good class/method/field/prop/auto names?

25. TIP: USE INVERSION OF CONTROL
Domain class constructor takes interface
parameters only (C#)
Don’t new domain class from within domain class
(fine to new framework classes e.g. List<T>,
Hashset<T> etc)
Why? Testing class A would be implicit test of B as well
Constructor stores interface parameter in field
Constructor does nothing else
Why? Interface can easily be mocked therefore easy to
test
Use 2-phase construction via Initialize() method if needed

26. INVERSION OF CONTROL DEMO

27. TIP: AVOID CODE COMMENTS
Comments are very useful for big and complicated things
Warning: Comments quickly get out of date with respect to
code during refactor
Comments not necessary for small and easy to understand
things
Corollary: Only create small, easy to understand well
named things and therefore ditch comments

28. TIP: AVOID EXCESSIVE NULL CHECKING
Excessive null checking is a Code smell
if (dog != null) {} OR if (dog == null)
Consider Null Object Pattern

29. DEMO NULL OBJECT PATTERN

30. TIP: CONFORM TO A SIMPLE CODE
STANDARD
Author a 1 page annotated coding standard
Why? If it all looks like it was written by one person then
it’s going to be easier maintain/learn
Get dev buy-in by building team consensus on
content
Print it off for everyone to put on the wall by their desk
Police it with code review
Use tooling: e.g. Write a Resharper standard and share
with the team

31. TIP: PRACTICE INTERFACE BASED
PROGRAMMING
Every domain class should should be accompanied by an
interface
What is a domain class?
One that has behaviour
Pass IDogController around, not DogController
Why? Decrease coupling between classes

32. TIP: USE MULTIPLE METHOD RETURNS
In the old days single method return was 
Why? Because of long complicated methods in God classes
Requires carefully nested method if/else hierarchy
If you don’t have God classes with long complicated
methods then you have no fear of multiple method returns
any more 
Why? Simpler to read due to dramatic reduction in nested
if/else hierarchy

33. TIP: AVOID C# REGIONS
Regions (#region) are a great place to hide code 
Often commented out code can be found hiding in them
God classes often lurk within regions pretending to not be
God classes Grrrrr

34. TIP: AVOID SPECULATIVE GENERALITY
App developers are often wannabe framework developers
Allow base classes to emerge from ongoing requirements
Don’t try and predict the future now
Avoid marking a method as virtual unless there is a class
to override it right now

35. TIP: BUY RESHARPER LICENSES
All C# devs should use ReSharper
Essential for quick and accurate refactoring
Set up shared team coding style
Reformat class(es) automatically before check-in
Find type
Find implementation of interface/method
Refactor name of class/method/field/auto etc

36. TIP: LEARN ALL LANGUAGE FEATURES
Polymorphism: check
Interface based programming: check
Generics: check
Iterators: check
LINQ: check
async/await: check
C#

37. TIP: HIRE QUALITY-MINDED ENGINEERS
Do they care about code quality? Ask them!
When was the last time they checked-in a unit test?
Prove it! Get them to write an algorithm on the white
board and a unit test for it
Get them to come up with the list of tests they would write
for the algorithm
Ensure good CS background: data structures & algorithms
Make sure they really know all the latest stuff (passion)
Never hire a ‘maybe’
Ensure good team fit – everyone meets the candidate

38. CALL TO ACTION
Code quality directly impacts $takeholder through to end
user experience
Up the ante: Make code quality your mission
Write good quality unit tests
Maintain a hygienic code base (inc tests)
Build a legacy your team is proud of that your users will
love

39. REFERENCES
Clean Code: A Handbook of Agile Software Craftsmanship,
Robert C Martin aka Uncle Bob
Awesome google talk (Misko Hevery)
http://www.youtube.com/watch?v=acjvKJiOvXw