Don't be STUPID, Grasp SOLID - North East PHP
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The document discusses object-oriented programming and APIs. It contrasts the "classic view" of objects representing physical things with the "modern view" of objects representing collections of related behaviors. Well-designed APIs follow principles like single responsibility, open/closed design, and dependency inversion. Poorly designed APIs exhibit issues like global state, tight coupling, duplication, and premature optimization. The talk emphasizes that object-oriented patterns like polymorphism, encapsulation, and applying SOLID principles result in modular, reusable, and maintainable code, though at a higher initial cost.
Don't be STUPID, Grasp SOLID - North East PHP
- 1. Don’t Be STUPID Grasp SOLID! Anthony Ferrara NorthEastPHP 2013
- 4. Classic View Object == Physical “Thing”
- 5. Classic View Object == Physical “Thing” Methods == Actions on “Thing”
- 6. Classic View Object == Physical “Thing” Methods == Actions on “Thing” Properties == Description of “Thing”
- 7. Animal MammalBird Fish CatCow Dog Lion Feline Cheetah
- 8. Classic View $lion = new Lion; $lion->roar(); $lion->walkTo($point); $lion->hunt($zebra); $lion->sleep();
- 10. Classic View $lion = new Lion; $lion->roar(); $lion->walkTo($point); $lion->hunt($zebra); $lion->sleep();
- 11. Classic View $lion = new Lion; $lion->roar(); $lion->walkTo($point); $lion->hunt($zebra); $lion->sleep(); Does A Lion Have A Button To Make It Roar?
- 12. Classic View $lion = new Lion; $lion->roar(); $lion->walkTo($point); $lion->hunt($zebra); $lion->sleep(); Does A Lion Have A Button To Make It Roar?What Does It Mean For An Object To “Hunt”?
- 13. Classic View $lion = new Lion; $lion->roar(); $lion->walkTo($point); $lion->hunt($zebra); $lion->sleep(); Does A Lion Have A Button To Make It Roar?What Does It Mean For An Object To “Hunt”? What Is A Lion In Relation To Our Application?
- 14. The Classical Model Is Easy To Understand
- 17. “Modern” View Object == Collection Of (Related) Behaviors
- 18. “Modern” View Object == Collection Of (Related) Behaviors Methods == Behavior
- 19. “Modern” View Object == Collection Of (Related) Behaviors Methods == Behavior Properties == Details Of Behavior
- 20. Classic View == “(conceptually) is a” Modern View == “behaves as a”
- 21. interface Number { function getValue(); function __toString(); function add(Number $n); function subtract(Number $n); function equals(Number $n); function isLessThan(Number $n); function isGreaterThan(Number $n); }
- 22. Number IntegerFloat Decimal longshort long long unsigned signed
- 23. But Wait!
- 24. We Don’t Even Need Inheritance
- 25. All We Need Is Polymorphism And Encapsulation
- 27. Polymorphism Behavior Is Determined Dynamically “Dynamic Dispatch”
- 28. Procedural Code if ($a instanceof Long) { return new Long($a->getValue() + 1); } elseif ($a instanceof Float) { return new Float($a->getValue() + 1.0); } elseif ($a instanceof Decimal) { return new Decimal($a->getValue() + 1.0); }
- 29. Polymorphic Code return $int->add(new Integer(1));
- 30. Polymorphic Code class Integer implements Number { public function add(Number $a) { return new Integer( $this->getValue() + (int) $a->getValue() ); } }
- 31. Polymorphic Code class Float implements Number { public function add(Number $a) { return new Float( $this->getValue() + (float) $a->getValue() ); } }
- 32. Encapsulation Behavior Is Completely Contained By The Object’s API (Information Hiding)
- 33. Procedural Code if (5 == $number->value) { print “Number Is 5”; } else { print “Number Is Not 5”; }
- 34. Encapsulated Code if ($number->equals(new Integer(5))) { print “Number Is 5”; } else { print “Number Is Not 5”; }
- 35. Encapsulated Code class Decimal implements Number { protected $intValue; protected $exponent; public function equals(Number $a) { if ($a instanceof Decimal) { // Compare Directly } else { // Cast } } }
- 36. Behavior Is Defined By The API
- 37. Two Types Of Primitive APIs Interfaces (Explicit)
- 38. Two Types Of Primitive APIs Interfaces (Explicit) Duck Typing (Implicit)
- 39. If an Object Is A Collection Of Behaviors...
- 40. What Is A Collection Of Classes/Objects?
- 41. APIs Method
- 44. APIs Method MethodMethod Class ClassClass Package PackagePackage Library
- 45. APIs Method MethodMethod Class ClassClass Package PackagePackage Library Framework LibraryLibrary
- 47. What Makes A Good API?
- 48. A Good API Does One Thing
- 49. A Good API Never Changes
- 50. A Good API Behaves Like Its Contract
- 51. A Good API Has A Narrow Responsibility
- 52. A Good API Depends Upon Abstractions
- 54. S - Single Responsibility Principle O- L - I - D- A Good API Does One Thing
- 56. S - Single Responsibility Principle O- Open / Closed Principle L - I - D- A Good API Never Changes
- 58. S - Single Responsibility Principle O- Open / Closed Principle L - Liskov Substitution Principle I - D- A Good API Behaves Like Its Contract
- 62. S - Single Responsibility Principle O- Open / Closed Principle L - Liskov Substitution Principle I - Interface Segregation Principle D- A Good API Has A Narrow Responsibility
- 64. S - Single Responsibility Principle O- Open / Closed Principle L - Liskov Substitution Principle I - Interface Segregation Principle D- Dependency Inversion Principle A Good API Depends Upon Abstractions
- 66. S - Single Responsibility Principle O- Open / Closed Principle L - Liskov Substitution Principle I - Interface Segregation Principle D- Dependency Inversion Principle
- 67. Note That SOLID Does Not Dictate What Is Good OOP
- 68. SOLID Emerges From Good OOP
- 70. So, What Makes A Bad API?
- 71. Global Variables (Spooky Action At A Distance)
- 72. Depending On Specifics Of An Implementation
- 76. Duplication
- 78. S - Singletons T - U - P - I - D- Global Variables (Spooky Action At A Distance)
- 80. S - Singletons T - Tight Coupling U - P - I - D- Depending On Specifics Of An Implementation
- 82. S - Singletons T - Tight Coupling U - Untestable Code P - I - D- Hidden Dependencies
- 84. S - Singletons T - Tight Coupling U - Untestable Code P - Premature Optimization I - D- Unhealthy Focus On Performance
- 86. S - Singletons T - Tight Coupling U - Untestable Code P - Premature Optimization I - Indescriptive Naming D- Poorly Named APIs
- 88. S - Singletons T - Tight Coupling U - Untestable Code P - Premature Optimization I - Indescriptive Naming D- Duplication Duplication Duplication DuplicationDuplication Duplication Duplication Duplication Duplication
- 90. S - Singletons T - Tight Coupling U - Untestable Code P - Premature Optimization I - Indescriptive Naming D- Duplication
- 92. What Good OOP Gives You Modular Code Reusable Code Extendable Code Easy To Read Code Maintainable Code Easy To Change Code Easy To Understand Code Clean Abstractions (mostly)
- 93. What Good OOP Costs You Tends To Have More “Layers” Tends To Be Slower At Runtime Tends To Have Larger Codebases Tends To Result In Over-Abstraction Tends To Require More Effort To Write Tends To Require More Tacit Knowledge
- 94. Let’s Look At Some Code!
- 95. interface Car { public function turnLeft(); public function turnRight(); public function goFaster(); public function goSlower(); public function shiftUp(); public function shiftDown(); public function start(); }
- 96. interface Steerable { public function steer($angle); } interface Acceleratable { public function accelerate($amt); } interface Shiftable { public function shiftDown(); public function shiftUp(); }
- 97. interface Transmission { public function getNumberOfGears(); public function getGear(); public function shiftToNeutral(); public function shiftToReverse(); public function shiftToGear($gear); } interface Manual extends Transmission { public function engageClutch(); public function releaseClutch(); } interface Automatic extends Transmission { public function shiftToDrive(); }