Slides about Robert C. Martins book "Clean Code: A Handbook of Agile Software Craftsmanship". (PDF version)

1. Clean Code
Hendrik Ebel
10. Mar. 2009
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2. Topics
Motivation
Meaningful Names
Comments
Functions
By Robert C. Martin & Co.
Objects and Data Structures Object Mentor Inc.
Error Handling
Unit Tests
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3. What is Clean Code?
One Question ...
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4. What is Clean Code?
One Question ...
elegant
efficient
simple and direct
readability easy to enhance
like a well-written prose
care
no duplications
was made for the problem
...many answers!
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5. What is Clean Code?
One Question ...
elegant
efficient
simple and direct
readability easy to enhance
like a well-written prose
care
no duplications
was made for the problem
...many answers!
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6. Motivation
The Total Cost of Owning a Mess
productivity vs. time
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7. Aims of Clean Code
producing better code
@author writing for readers
code has to be kept clean over time
„Leave the campground cleaner than
you found it.“
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8. Meaningful Names
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9. Meaningful Names
variable, function or class names should
answer all the big questions:
why it exists?
what it does?
how it is used?
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10. Meaningful Names
If a name requires a comment, then the
name does not reveal its intent
avoid disinformation
don't use type information in names
(example: personList)
Spelling similar concepts similarly is
information. Using inconsistent spellings is
disinformation.
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11. Comments
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12. Good and Bad Comments
•Public API Comments •Redundant Comments
•Legal Comments •Noise Comments
•Explanation of Intent •Position Markers
•Warning for •Closing Brace Comments
Consequences •Commented-Out Code
•real TODO Comments •Obsolete Comments
•Nonpublic JavaDocs
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13. Comments
„Purpose of a comment is to explain code
that does not explain itself.“
Comments do not make up for bad code
Don‘t use a comment when you can use a
function or a variable
Comments can contains lies
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14. Functions
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15. Functions
The goal is to tell the story of the
system.
„The first rule of functions is that they
should be small.“
Do One Thing!
Stepdown Rule
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16. Functions
Ideal number of arguments is zero
More than three should‘t be used
anyway
Flag arguments are ugly.
Avoid output arguments
Side effects are lies.
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17. Objects and Data
Structures
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18. Objects
hide data and expose functions
easy to add new objects
hard to add new behaviors
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19. Data Structures
expose data and have no meaningful
functions
easy to add new behaviors
hard to add new data structures
Choose the approach that is best for the job.
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20. Error Handling
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21. Error Handling
Write code that is clean and rebust
See error handling as a separate concern
Use exceptions rather than return codes
Use unchecked exceptions
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22. Error Handling
Don‘t return NULL
throwing an exception or a special
case object like
„Collections.emptyList()“
Don‘t pass NULL
InvalidArgumentExceptions or assert
better: forbid passing NULL by default
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23. Unit Tests
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24. Unit Tests
Test Driven Development (TDD)
test and production code are written
together
tests just a few seconds ahead
Keeping tests clean
Test code is just as important as
production code.
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25. Unit Tests
One Assert or Single Concept per Test
F.I.R.S.T.
Fast
Independent
Repeatable (in any environment)
Self-Validation
Timly
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26. Thanks - Any Questions?
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27. Sources
Book
„Clean Code“ by Robert C. Martin
ISBN: 0132350882
Images
http://www.failblog.org
http://www.flickr.com/photos/hugovk/199425487/
http://www.flickr.com/photos/jackpot321/1809424991/
http://www.osnews.com/story/19266/WTFs_m
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