Kotlin Study group # 3 Inheritance Ref book: Kotlin A Brain-Friendly Guide

1. Inheritance
Kotlin Study Group #3
Andy Lu
2021.04.08

2. Who am I
Andy Lu
Android Engineer in FutureDial
第二屆 Kotlin 讀書會導讀者
❤ Kotlin
❤ Flutter
Medium: https://medium.com/@andyludeveloper
2

3. Agenda
● What’s inheritance?
● When inherited?
● How to inherit?
○ Superclass/Base class
○ Subclass/Derived class
○ Any
● Q&A 3

4. What’s inheritance?
4

5. What’s inheritance?
5
Student Class Teacher Class

6. What’s inheritance?
6
Student Class Teacher Class
Same
properties
Same
function

7. What’s inheritance?
7
Superclass/ base class
Subclass/ derived class

8. What’s inheritance?
8
● To avoid duplicate code.
● Override functions and
properties.
● Subclass can add own
functions or properties.

9. When inherit?
9

10. is-a relationship
10

11. 11
● Student is a People. ✅
is-a relationship

12. 12
● Student is a People. ✅
● Teacher is a People. ✅
is-a relationship

13. 13
● Student is a People. ✅
● Teacher is a People. ✅
● Tiger is a People. ❌
is-a relationship

14. 14
● Student is a People. ✅
● Teacher is a People. ✅
● Tiger is a People. ❌
● Aircraft is a People. ❌
is-a relationship

15. How to inherit?
15

16. 16
Superclass/ base class
Subclass/ derived class
Inheritance tree

17. Superclass/Base class
17

18. Class
18

19. Can not be inherited
19

20. Can not be inherited
20
��

21. Superclass
21

22. Superclass
22
Add open keyword

23. Can be inherited
23
��

24. Subclass/Derived class
24

25. How to inherit?
25

26. Inherit a superclass
26

27. Inherit a superclass
27
: superclass name (constructor)

28. Advantage
28
1. Can access all open functions and properties
from superclass.
2. Can override all open functions or properties.
3. Can create own functions or properties.

29. Access
29

30. Access
30

31. Access
31
Hello, my name is Andy

32. Not allow to access
32
private keyword make function non-accessible

33. Not allow to access
33

34. Override
34

35. Override
35

36. Override
36
1. Add open keyword

37. Override
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1. Add open keyword
2. Use override keyword

38. Override
38
Student Andy say hi

39. Create
39

40. Create
40

41. Create
41
Andy is doing home work

42. Create
42

43. Thinking
43
❓

44. Thinking
44

45. Any Class
45

46. Any class
46

47. Any class
47
● equals()
● hashCode()
● toString()

48. Q & A
48

49. 49
Next Chapter:
abstract classes and interfaces: Serious Polymorphism