tech talk for iOS meetup for August http://www.meetup.com/Singapore-iOS-Dev-Scout-Meetup/events/224367240/

1. Class or Struct
by Akira Hirakawa @ Burpple

2. which should I create?
class or struct?

3. What is the difference?

4. Apple says…

5. Both can
• Define properties
• Define methods
• Define subscripts
• Define initializers
• Be extended
• Conform to protocols

6. class can, struct can not
• Inheritance
• Type casting
• Deinitialize
• Reference counting
• class is allocated on heap, struct is on stack

7. Inheritance
struct SampleStruct {
var num = 0
}
// cannot:(
struct SampleStruct2: SampleStruct {
}

8. Reference counting
class SampleClass {
}
var array: [SampleClass] = ....
for p in array {
// increment reference counting
...
// decrement reference counting
}
struct SampleStruct {
}
var array: [SampleStruct] = ....
for p in array {
...
}

9. main difference is…

10. struct is Value Type

11. class is Reference Type

12. demo

13. so,which should I create?
class or struct?

14. Apple says…

15. create struct, when…
• data structure is simple
• properties are value type(struct)
• purpose is not to update itself, when data is
passed to a method

16. ex: CGPoint
public struct CGPoint {
public var x: CGFloat
public var y: CGFloat
public init()
public init(x: CGFloat, y: CGFloat)
}
• data structure is simple
• properties are value type
• purpose is not to update itself, when data is
passed to a method

17. be careful of creating
struct, when …

18. many properties
• That struct is value type means it’s copied when
assigned
• the more properties a struct has, the more
memory machine needs, when copied

19. class object in struct
demo

20. Struct
• String
• Array
• Dictionary
• Bool
• Int
• Double
• Float

21. different from other
languages

22. performance?

23. case 1
small class VS small struct
just create instance

24. case 2
class with properties VS struct with properties
just create instance

25. case 3
call method with parameter

26. case 4
NSArray VS Array

27. case 5
Array<class> VS Array<struct>

28. Summary
• having few properties is better for struct
• “struct or class” depends on purpose
• ex: class can be used for Data object from API
• ex: struct can be used for Request data to API

29. Akira Hirakawa
http://akirahrkw.xyz
https://github.com/akirahrkw
Thanks:)