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Object Oriented Programming in Swift Ch1 - Inheritance
- 1. Object Oriented Programming inSwift Ch 1: Inheritance Sai Li @ Yowoo Tech. 2016/12/5
- 2. References • Agile SoftwareDevelopment: Principles, Patterns, and Practice ( : ) by Robert C. Martin • Fundamental Object Oriented Programming by Hsuan-Tien Lin • by Teddy Chen • Essential Object-Oriented Programming by Josh Ko
- 3. OOP • Encapsulation • Inheritance •Polymorphism
- 4.
- 5.
- 6. Has-A • Has-A: abasic way to reuse variables/methods in other classes
- 7. Has-A • Has-A: abasic way to define components of a system • iPhone has a camera
- 8. Has-A • Has-A: abasic mechanism for objects to connect with each other • He has 2 friends: Tom and Jerry
- 9. Has-A: most basicdesign component of OOP
- 10. chi • Admin isa user • can be implemented via has-a: Everyone has Brokeback Mountain in mind child
- 11. • Type Ainherit TypeB: TypeA is a (special case of) TypeB • TypeSubClass (TypeDerivedClass or ChildClass) inherit TypeSuperClass (TypeBaseClass or ParentClass)
- 12.
- 13. Uses of Is-A •CDAndCassetePlayer is a CassettePlayer
- 14. Uses of Is-A •CassettePlayer is a (concrete type of) Player • CDPlayer is a (concrete type of) Player
- 15. Uses of Is-A •CDplayer is a (update of) CassettePlayer • some behaviors “changed” • no as clear as the previous case, but a potential trick in OOP
- 16. • Multiple inheritance:Not supported in Swift • Swift: single inheritance (Java)
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- 19. Is-A • is anextended type of - FunPerson is Person who can tell jokes • is a more concrete/restricted description of - YoungPerson is Person who is young • (is an update of) - NewStaff replaces ExistingStaff
- 21. • Over-use ofinherit for is-a: 1 class -> 1 instance • Usual goal of OOP: one class, many instances
- 22. Is-A • Under-user ofinherit for is-a: overly complicated class YowooStaff • Bugs/hacks? cali = YowooStaff(id: “”, name: “CYLi”, title: “CFO”)
- 23.
- 24. Instance Variables andInheritance • Staff: 1 instance variables • YowooStaff: 2 instance variables
- 25. Instance Variables andInheritance
- 26. • instance variablebinding: determined at compile time • same “name” can NOT co-exist in a class, binding determined by compile-time type.
- 27. Instance Methods andInheritance • Staff: 1 instance method • RD: 2 instance methods
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- 29. • instance methodbinding: dynamic, depending on run-time instance types
- 30. Reference Assignment • saiLiis an instance of GoodStudent • saiLi is an instance of Student, too • one instance, many coherent types
- 31. Constructor and Inheritance •initialize self first, ancestor last • the GoodStudent part of the memory initialized first, the Student part
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- 34. Private Variables andInheritance
- 35. private variables arestill “inherited” in memory, but not “visible” to the subclass because of encapsulation (security)
- 36. • protected: accessibleto Child(subclass)
- 37. • public: everyone •internal (default): same package classes • protected: sub-classes • private: class self Swift Access Permissions
- 38. Access Permission (Swift) •Child: same or more close than Parent
- 39. References • Apple: AccessControl and protected • http://commons.oreilly.com/wiki/images/a/a7/ Beyond_Java_I_2_tt13.png • https://upload.wikimedia.org/wikipedia/commons/ thumb/4/47/C3_linearization_example.svg/600px- C3_linearization_example.svg.png • https://developer.apple.com/library/content/ documentation/Swift/Conceptual/ Swift_Programming_Language/Art/ initializerDelegation02_2x.png