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SOLID and Clean Code with life project example
- 1. Datascope Systems Ltd. Howto write meaningful code
- 2. Bullet Points SOLID •Single Responsibility Principle • Open/Closed Principle • Liskov Substitution Principle • Inversion Of control • Dependency Inversion Principle POLA Demeter Law Lowering Principle Live project example
- 3. Single Responsibility principle Theclass has only one reason to change! Repository – is that a good example? What if persistence mechanism for saving/retrieving business entities will be changed separately? CQRS! Facade pattern for interacting with printing subsystem.
- 4. RFID Facade example Classhas more than 1 responsibility, but only one reason to change.
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- 6. Open-Closed principle Modules shouldbe open for extension but closed to modification
- 7. Barbara-Liskov substitution principle x(O) =y(O) if Y is type of T, and T is derived from X a subtype of X
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- 9. Interface Segregation Principle Let’s imaginewe have an interface which is pretty much the same as a sub-repository
- 10. This is howsaving/loading supposed to look like And Boooooom, at some point business requires only read-only settings Interface Segregation Principle
- 11. Load probably willbe similarly to that then … And start from here we have breach ISP. Client should not depend on any method he is not using Interface Segregation Principle
- 12. Solution: split intotwo interfaces Interface Segregation Principle
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- 14. Dependency Inversion Principle Exampleof inversion of control in DB is a many to many relation. Order has no idea of OrderDetails existence. As long as you have a magic word 1) using i.e C# 2) import i.e. Java 3) include i.e C,C++ You have an arrow pointing from you (you are depend on smth…)
- 15. Examples Time to goReal…
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- 17. DeliveryCollectionHelper vs POLA andSRP ФабричноЛоггеровыйКартинкоДоставочноСервисныйХелпер
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- 19. Let’s apply somerefactoring Get rid of unnecessary dependencies and apply SRP. Lowering Law, Internal Coupling, Descriptors and Views (Logical diff), Refactoring stages
- 20. OCP Unnecessary coupling (Class containstwo services), horizontal dependencies, try to avoid that
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- 23. Strategy is ready,but still something is wrong??? Proper Factory
- 24. Usage of Factoryand Strategies example
- 25. Test is prettydamn simple
- 26. What`s wrong here? Classusage example: Class definition (object will goes down to service layer):
- 27. Demeter law inaction • Each unit should have only limited knowledge about other units: only units "closely" related to the current unit. • Each unit should only talk to its friends; don't talk to strangers. • Only talk to your immediate friends.
- 28. Demeter law inaction
- 29. What about up/downcasting through explicit operator? Hide SP’s - Sort of ACL
- 30. Right way ofdoing it (this is service layer)
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- 36. DI in action(diff between DIP and Dependency Injection)
- 37. DI in action(more complicated example) What if you need sort of magnet objects like reports, user roles, email generators etc. So, how to invert arrows ? How to get rid of using, import etc in target class
- 38. DI in action(report example) Dependency diagram you want to achieve:
- 39. DI in action(report example) Reports side effect (two reports 99% equals) This is how it looks like in practice:
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- 41. Report Collector inaction
- 42. My LSP mistakein Quilt project
- 43. Software Development isamazing!