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Object Calesthenics

Object Calesthenics

Thunder talk hold at SilverStripe Europe Conference in Malta 2017.

wernerkrauss

October 14, 2017
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  1. Object Calesthenics
    14.10.2017 www.silverstrip.es 1

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  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

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  3. Focus on
    • Maintainability
    • Readability
    • Testability
    • Comprehensibility
    • Reusability
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  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

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  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
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  6. OMFG!
    • Method does too
    much
    • Hard to understand
    • Repeated code
    – Who copy/pasted that?
    14.10.2017 www.silverstrip.es 6

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  7. Clean it up
    • Duplicated code
    extracted and now
    reusable
    • Easier to
    understand
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  8. #2: No Else Keyword
    No!
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  9. NEVER EVER
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  10. 14.10.2017 www.silverstrip.es 12
    You never come here when you
    have a $fieldName

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  11. Possible Solution
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    Return early
    Single path, no logal tree.

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  12. #3: Wrap Primitives and Strings
    • If it has behaviour
    • Encapsulate primitives within Objects
    • Better Type Hinting
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  13. Do you remember?
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  14. Much cleaner nowadays
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  15. #4: Use First Class Collections
    • SilverStripe has ArrayList
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  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

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  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

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  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

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  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

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  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

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  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

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  22. #10: Document Your Code
    • Don‘t explain bad code, fix it!
    • Mark @todo items
    • Automatic API docs possible
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  23. #11: Test your code
    • „Stupid“ mistakes are found faster
    • Easier refactoring
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  24. Sources
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  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

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  26. Thank you!
    www.silverstrip.es
    14.10.2017 www.silverstrip.es 28

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