Object Calesthenics

Thunder talk hold at SilverStripe Europe Conference in Malta 2017.

Transcript

1. Object Calesthenics
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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
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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
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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?
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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
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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
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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
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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
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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
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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
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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
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26. Thank you!
    www.silverstrip.es
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