Transcript
Class or Structby Akira Hirakawa @ Burpple
which should I create? class or struct?
What is the difference?
Apple says…
Both can• Define properties
• Define methods
• Define subscripts
• Define initializers
• Be extended
• Conform to protocols
class can, struct can not
• Inheritance
• Type casting
• Deinitialize
• Reference counting
• class is allocated on heap, struct is on stack
Inheritance
struct SampleStruct { var num = 0 }
// cannot:( struct SampleStruct2: SampleStruct { }
Reference countingclass SampleClass { } var array: [SampleClass] = .... for p in array { // increment reference counting ... // decrement reference counting }
struct SampleStruct { } var array: [SampleStruct] = .... for p in array { ... }
main difference is…
struct is Value Type
class is Reference Type
demo
so,which should I create? class or struct?
Apple says…
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
ex: CGPointpublic 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
be careful of creating struct, when …
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
class object in struct
demo
Struct• String
• Array
• Dictionary
• Bool
• Int
• Double
• Float
different from other languages
performance?
case 1
small class VS small struct
just create instance
case 2
class with properties VS struct with properties
just create instance
case 3
call method with parameter
case 4
NSArray VS Array
case 5
Array<class> VS Array<struct>
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
Akira Hirakawa http://akirahrkw.xyz
https://github.com/akirahrkw
Thanks:)
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