Writing SOLID Code
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Presentation in Bulgarian about SOLID design principles. Presented at PlovDev Conference 2014, ProxiAD office in Bulgaria (multiple times) and at an event for Woman Who Code in Sofia in 2017
Writing SOLID Code
- 1. kgolev.com@kotseto Writing SOLID Code Kostadin Golev CTO @ Rewards Labs 亠舒亰从舒亰 亠仍亠仄亠仆亳 仆舒 舒亰亢亟亠仆亳亠
- 2. kgolev.com@kotseto 仂亞舒仄亳舒仄 > 10 亞仂亟亳仆亳 仂亠亳仂仆舒仍仆亳亠 仄亳 亳仆亠亠亳 于从仍ﾑ于舒 gile, DevOps 亳 Test automation. 仂亟 弍舒舒 仆舒 亟于亠 亟亠舒. 弍亳舒仄 亟舒 仗亳舒, 弍仍仂亞舒 仄亳 亠 仆舒仄亳舒 仆舒 kgolev.com
- 4. kgolev.com@kotseto S ingle Responsibility Principle O pen-Closed Principle L iskov Substitution Principle I nterface Segregation Principle D ependency Inversion Principle
- 6. kgolev.com@kotseto 仆仄亠仆亳 亳仍亳 亳亟亠亳 仂仄舒亞舒 亟舒 于亰亳仄舒仄亠 仗仂-亟仂弍亳 亠亠仆亳 亳仍仂亢亳仄亳 舒 于 仄仆仂亞仂 亳 舒亰仍亳仆亳 亳舒亳亳 仂仄舒亞舒 亟舒 从仂仄仆亳从亳舒仄亠 仗仂-亟仂弍亠 从仂 亳仄舒 仆亠仂, 从仂亠仂 仆亳 舒亠于舒 亳仍亳 仆亠 仆亳 舒亠于舒 于 仆舒亳 亟亳亰舒亶仆, 仄仆仂亞仂 亠仂 仄仂亢亠仄 亟舒 仆舒仄亠亳仄 仗亳仆亳仗, 从仂亶仂 亟舒 亞仂 仂弍仆亳仄
- 7. kgolev.com@kotseto 舒亶 于舒仆, 从从舒舒 亳 于亠仆亳仍舒仂舒
- 9. kgolev.com@kotseto 磻舒 舒 仂 于舒亳 从仂亟 磡于舒 亟舒 仗舒于亳 亠亟仆仂 仆亠仂 亳 亟舒 亞仂 仗舒于亳 亟仂弍亠
- 10. kgolev.com@kotseto 仂亟舒 磡于舒 亟舒 亳仄舒 舒仄仂 亠亟仆舒 仗亳亳仆舒 亟舒 亠 仗仂仄亠仆亳
- 11. kgolev.com@kotseto class TaxiService { void orderTaxi(String phone, String address) { if (phone.length() < 7) { throw new BadPhoneNumberException (Phone not valid!"); } taxiPool.sendTaxi(address); smsClient.sendMessage(phone, "Your taxi is on the way!"); }
- 12. kgolev.com@kotseto class TaxiService_V2 { void orderTaxi(String phone, String address) { if (phone.length() < 7 && phone.length() > 12) { // <-- mistake throw new BadPhoneNumberException (Phone not valid!"); } taxiPool.sendTaxi(address); smsClient.sendMessage(phone, Your taxi is on the way!"); }
- 13. kgolev.com@kotseto boolean phoneIsNotValid(String phone) { return phone.length() < 7 || phone.length() > 12; }
- 14. kgolev.com@kotseto public class { public boolean phoneIsNotValid(String phone) { return phone.length() < 7 || phone.length() > 12; } }
- 15. kgolev.com@kotseto class TaxiService_V3 { void orderTaxi(String phone, String address) { if (smsService.phoneIsNotValid(phone)) { throw new BadPhoneNumberException ("Phone not valid!"); } taxiPool.sendTaxi(address); smsService.sendMessage(phone, Your taxi is on the way!"); }
- 16. kgolev.com@kotseto 仂亟舒 于亳 亠 亟仍亞 亳 仗舒于亳 仄仆仂亞仂 仆亠舒 丐亟仆仂 于亳 亠 亟舒 仂弍仆亳亠 从舒从于仂 仗舒于亳 亠亟仆仂 仗舒亠 从仂亟 仄亠仂 仆舒 仄亠仂亟舒/从仍舒舒 从仂亶仂 仗亳亠亠 仆礆舒 仂弍仂 从仂亟舒, 从仂亶仂 舒亰舒弍仂于舒亠
- 19. kgolev.com@kotseto 弌仂亠舒 磡于舒 亟舒 弍亟亠 亰舒于仂亠仆 亰舒 仄仂亟亳亳从舒亳, 仆仂 仂于仂亠仆 亰舒 仆舒亟亞舒亢亟舒仆亠
- 20. kgolev.com@kotseto Customer silverCustomer = new Customer(SILVER); getDiscountAmount(100, silverCustomer); // 10 Customer goldenCustomer = new Customer(GOLD); getDiscountAmount(100, silverCustomer); // 20
- 21. kgolev.com@kotseto double getDiscountAmount (int purchaseTotal, Customer customer) { double discount = 0; switch (customer.type()) { case SILVER: discount = 0.1; break; case GOLD: discount = 0.2; break; } return discount * purchaseTotal; }
- 22. kgolev.com@kotseto class Customer { double getDiscount() { return 0; } }
- 23. kgolev.com@kotseto class SilverCustomer extends Customer { @Override double getDiscount() { return 0.1; } } class GoldenCustomer extends Customer { @Override double getDiscount() { return 0.2; } }
- 24. kgolev.com@kotseto double getDiscountAmount_V2 (int purchaseTotal, Customer customer) { return customer.getDiscount() * purchaseTotal; }
- 25. kgolev.com@kotseto 仂弍舒于礌亠仂 仆舒 仆仂于舒 仆从亳仂仆舒仍仆仂 亳亰亳从于舒 仄仆仂亢亠于仂 仗仂仄亠仆亳 于 舒 从仂亟, 于仄亠仂 仗亠亟亳仄仆仂 仗亳舒仆亠 仆舒 仆仂于
- 26. kgolev.com@kotseto 弌舒仍舒舒 从仂亰亠 亳亠仆亠
- 28. kgolev.com@kotseto 亠从亳 从仍舒, 从仂亶仂 仗亳亠仄舒 X 从舒仂 仗舒舒仄亠, 磡于舒 亟舒 仄仂亢亠 亟舒 舒弍仂亳 于亠从亳 仗仂亟从仍舒 仆舒 X
- 30. kgolev.com@kotseto interface Duck { void quack(); }
- 31. kgolev.com@kotseto class RealDuck implements Duck { @Override public void quack() { //quack code goes here! } }
- 32. kgolev.com@kotseto Duck realDuck = new RealDuck(); realDuck.quack(); //works!
- 33. kgolev.com@kotseto Duck duck = new ElectricDuck(); duck.quack(); //doesn't work?
- 34. kgolev.com@kotseto class ElectricDuck implements Duck { boolean turnedOn = false; public void quack() { if (turnedOn) { //quack code goes here! } } public void turnOn() { } }
- 35. kgolev.com@kotseto if (duck instanceof ElectricDuck) { ((ElectricDuck)duck).turnOn(); } duck.quack(); //now works!
- 36. kgolev.com@kotseto class ElectricDuck_V2 implements Duck { boolean turnedOn = false; public void quack() { if (!turnedOn) { turnOn(); } //quack code goes here! } public void turnOn() { } }
- 37. kgolev.com@kotseto Duck anyDuck = new AnyKindOfDuck(); anyDuck.quack(); //always works
- 38. kgolev.com@kotseto 舒从舒从仂: 仆亠 磡于舒 从仂亟舒 亟舒 于亳 亳亰仆亠仆舒亟舒
- 39. kgolev.com@kotseto 舒仄礌舒舒 仆舒 亳仗舒 仆舒 亠亟亳仆 从仍舒 仗仂仄亠仆 仗仂于亠亟亠仆亳亠仂 仄 舒仍舒亞舒 亠 亟舒 仗仂于亠磦舒仄亠 亳仗舒, 亰舒 亟舒 亳亰弍亠亞仆亠仄 仆亠亢亠仍舒仆仂 仗仂于亠亟亠仆亳亠
- 42. kgolev.com@kotseto 亠 仗亳仆亢亟舒于舒亶亠 仆亳从仂亶 亳 仆亳仂 亟舒 亰舒于亳亳 仂 亳仆亠亠亶 从仂亶仂 仆亠 仄 亠 仆亢亠仆
- 43. kgolev.com@kotseto interface Parent { void takeCareOfChildren(); } interface Programmer { void code(); } interface Driver { void drive(); }
- 44. kgolev.com@kotseto class Kostadin implements Parent, Programmer, { void takeCareOfChildren(); void code(); }
- 46. kgolev.com@kotseto 仂仍礆 亳仆亠亠亶 仄仆仂亞仂 仄亠仂亟亳 舒亰仆舒 亳仄仗仍亠仄亠仆舒亳 仆舒 仄亠仂亟 仂 亳仆亠亠亶, 从仂亶仂 亳亰仗仂仍亰于舒仄亠
- 47. kgolev.com@kotseto The Open Source Library
- 49. kgolev.com@kotseto 弌仄礌舒舒 仆舒 亟于亳亞舒亠仍 仆亠 磡于舒 亟舒 于仂亟亳 亟仂 仄礌舒 仆舒 舒于仂仄仂弍亳仍舒 Depend upon abstractions Do not depend on concretions
- 50. kgolev.com@kotseto class OpelDiesel { OpelDieselEngine engine; OpelDiesel() { engine = new OpelDieselEngine(); } void start() { engine.ignition(); } }
- 51. kgolev.com@kotseto class OpelGasoline { OpelGasolineEngine engine; OpelGasoline() { engine = new OpelGasolineEngine(); } void start() { engine.ignition(); } }
- 52. kgolev.com@kotseto OpelDiesel car = new OpelDiesel(); car.start(); OpelGasoline carGasoline = new OpelGasoline(); carGasoline.start();
- 53. kgolev.com@kotseto class Opel { Engine engine; Opel(Engine engine) { this.engine = engine; } void start() { engine.ignition(); } }
- 54. kgolev.com@kotseto class OpelDieselEngine implements Engine { @Override public void ignition() { } }
- 55. kgolev.com@kotseto Opel dieselCar = new Opel(new OpelDieselEngine()); dieselCar.start(); Opel gasolineCar = new Opel(new OpelGasolineEngine()); dieselCar.start();
- 56. kgolev.com@kotseto Opel oldOpel = new Opel(new VolgaEngine(), new MoskvitchBrakes());
- 57. kgolev.com@kotseto 仂仄礌舒舒 亳仍亳 亟仂弍舒于礌亠 仆舒 仄仂亟仍 于仂亟亳 亟仂 仗仂仄亠仆亳 仆舒 仄仂亟仍亳亠, 从仂亳仂 亠亟 仆舒亟 仆亠亞仂 (仄礌舒 仆舒 从仂仍舒舒 亰舒舒亟亳 仆仂于 舒从仄仍舒仂) 仂亟仍亳 仆舒 仗仂-于亳仂从仂 仆亳于仂 (从仂仍舒), 亰舒于亳 仂 仂仆仂 仂仗亠亟亠仍亠仆亳 仄仂亟仍亳 仆舒 仆亳从仂 仆亳于仂 (亟于亳亞舒亠仍/舒从仄仍舒仂)
- 58. kgolev.com@kotseto Software should be soft! By De鍖nition