Object Calesthenics

Thunder talk hold at SilverStripe Europe Conference in Malta 2017.

1. Object Calesthenics 14.10.2017 www.silverstrip.es 1
2. Object… WHAT? • Cal • is • then • ics - /ˌkaləsˈTHeniks/ • Gymnastics • 9 +2 simple, formalised exercises • Invented by Jeff Bay in his book “The ThoughtWorks Anthology” • Adapted for PHP by Raphael Dohms 14.10.2017 www.silverstrip.es 2
3. Focus on • Maintainability • Readability • Testability • Comprehensibility • Reusability 14.10.2017 www.silverstrip.es 3
4. How to use it • Guidelines, not rules! • Pick one and start using it • Add the next items next 14.10.2017 www.silverstrip.es 4
5. #1: Only One Level Of Intendation Per Method • Better readability and understanding of the code • Extract code to reusable methods, that do one thing 14.10.2017 www.silverstrip.es 5
6. OMFG! • Method does too much • Hard to understand • Repeated code – Who copy/pasted that? 14.10.2017 www.silverstrip.es 6
7. Clean it up • Duplicated code extracted and now reusable • Easier to understand 14.10.2017 www.silverstrip.es 7
8. #2: No Else Keyword No! 14.10.2017 www.silverstrip.es 8
9. NEVER EVER 14.10.2017 www.silverstrip.es 9
10. 14.10.2017 www.silverstrip.es 12 You never come here when you have a $fieldName
11. Possible Solution 14.10.2017 www.silverstrip.es 13 Return early Single path, no logal tree.
12. #3: Wrap Primitives and Strings • If it has behaviour • Encapsulate primitives within Objects • Better Type Hinting 14.10.2017 www.silverstrip.es 14
13. Do you remember? 14.10.2017 www.silverstrip.es 15
14. Much cleaner nowadays 14.10.2017 www.silverstrip.es 16
15. #4: Use First Class Collections • SilverStripe has ArrayList 14.10.2017 www.silverstrip.es 17
16. #5: One Arrow Per Line • If not a getter or fluent • Otherwise hard to debug, test, read and understand • See Demeter‘s Law 14.10.2017 www.silverstrip.es 18
17. #6: Don‘t Abbrevate • Use clear and easy to understand names • Don‘t call your methods like your company or your cat‘s name (if it has nothing to do with it) • Your co-worker will thank you 14.10.2017 www.silverstrip.es 19
18. #7: Keep Your Classes Small • 100 lines per class (incl. Docblocks) • 15 classes per package (aka. namespace or folder) • Single Responsibility • Slimmer namespaces and folders 14.10.2017 www.silverstrip.es 20
19. #8: Max. 5 Instance Variables Per Class • SilverStripe specific config ($db etc…) does not count • Easier Mocking for tests • Less depencies 14.10.2017 www.silverstrip.es 21
20. #9: No Getters / Setters • Tell, don‘t ask • It‘s OK to use accessors to get a state • Any decision on the state should be made inside the object 14.10.2017 www.silverstrip.es 22
21. No Getters/Setters • Procedural code gets information then makes decisions. Object-oriented code tells objects to do things (Alec Sharp) • https://pragprog.com/articles/ tell-dont-ask 14.10.2017 www.silverstrip.es 23
22. #10: Document Your Code • Don‘t explain bad code, fix it! • Mark @todo items • Automatic API docs possible 14.10.2017 www.silverstrip.es 24
23. #11: Test your code • „Stupid“ mistakes are found faster • Easier refactoring 14.10.2017 www.silverstrip.es 25
24. Sources 14.10.2017 www.silverstrip.es 26
25. About me • Werner M. Krauß • Located in Hallstatt, Austria • wmk on IRC slack / github / stackoverflow • PHP since 1998 • Freelancer since 2006 (netwerkstatt) • SilverStripe since 2009 14.10.2017 www.silverstrip.es 27
26. Thank you! www.silverstrip.es 14.10.2017 www.silverstrip.es 28