Clean Code

Clean Code Hendrik Ebel 10. Mar. 2009 Tuesday, March 10, 2009

Topics Motivation Meaningful Names Comments Functions By Robert C. Martin & Co. Objects and Data Structures Object Mentor Inc. Error Handling Unit Tests Tuesday, March 10, 2009

What is Clean Code? One Question ... Tuesday, March 10, 2009

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! Tuesday, March 10, 2009

Motivation The Total Cost of Owning a Mess productivity vs. time Tuesday, March 10, 2009

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.“ Tuesday, March 10, 2009

Meaningful Names Tuesday, March 10, 2009

Meaningful Names variable, function or class names should answer all the big questions: why it exists? what it does? how it is used? Tuesday, March 10, 2009

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. Tuesday, March 10, 2009

Comments Tuesday, March 10, 2009

Good and Bad Comments • Public API Comments • Redundant Comments • Legal Comments • Noise Comments • Explanation of Intent • Position Markers • Warning for • Closing Brace Comments • Commented-Out Code Consequences • real TODO Comments • Obsolete Comments • Nonpublic JavaDocs Tuesday, March 10, 2009

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 Tuesday, March 10, 2009

Functions Tuesday, March 10, 2009

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 Tuesday, March 10, 2009

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. Tuesday, March 10, 2009

Objects and Data Structures Tuesday, March 10, 2009

Objects hide data and expose functions easy to add new objects hard to add new behaviors Tuesday, March 10, 2009

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. Tuesday, March 10, 2009

Error Handling Tuesday, March 10, 2009

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 Tuesday, March 10, 2009

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 Tuesday, March 10, 2009

Unit Tests Tuesday, March 10, 2009

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. Tuesday, March 10, 2009

Unit Tests One Assert or Single Concept per Test F.I.R.S.T. Fast Independent Repeatable (in any environment) Self-Validation Timly Tuesday, March 10, 2009

Thanks - Any Questions? Tuesday, March 10, 2009

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 Tuesday, March 10, 2009

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Clean Code

by Hendrik Ebel on Mar 10, 2009

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Clean Code — Presentation Transcript