/*
Extension
*/
class C{}
protocol someProtocol{}
protocol anotherProtocol{}
// extend protocol conformance
extension C:someProtocol,anotherProtocol{
//do something to conform the protocol
}
// extend computed property
extension C{
var number:Int{
return self.number*2
}
}
extension Double{
var km :Double { return self * 1_000.00 }
}
var qianmi = 25.3.km
print(qianmi)
/* extend initializer,
only convenience initializer for class not for struct
*/
/*
struct Point{
var x=0,y=0
}
struct Size{
var long=5,width=5
}
struct Rect{ // if I put class here it will fail
var point:Point=Point()
var size:Size=Size()
}
extension Rect{
init(center:Point,size:Size){
let orix=center.x - (size.long/2)
let oriy=center.y - (size.width/2)
self.init(point:Point(x:orix,y:oriy),size:size)
}
}
*/
struct Size {
var width = 0.0, height = 0.0
}
struct Point {
var x = 0.0, y = 0.0
}
class Rect {
var origin = Point()
var size = Size()
}
extension Rect {
convenience init(center: Point, size: Size) {
let originX = center.x - (size.width / 2)
let originY = center.y - (size.height / 2)
self.init(center: Point(x: originX, y: originY), size: size)
}
}
/*
Extension on method
*/
extension Int{
func repetitions(foo:()->Void){
for _ in 0..<self{
foo()
}
}
}
extension String{
func foo(){
print(self + self)
}
}
var a="god damn it"
a.foo()
a.self
3.self
3.repetitions {
print("hey")
//print(self)
// because this code block don't belong to 3 itself
// hence you can't put self here, because it's undeclared
}
// Extension on method to mutate instance itself
extension Int{
mutating func double(){
self=self*2 // because by default, self is immutable
}
}
/*
extension for subscript
*/
extension Int{
subscript(index:Int) -> Int {
var decimalBase = 1
for _ in 0 ..< index{
decimalBase *= 10
}
return (self/decimalBase)%10
}
}
12345[0]
12345[1]
extension Int{
enum Kind{
case negative,zero,positive
}
var kind:Kind{
switch self{
case 0:
return .zero
case let x where x > 0:
return .positive
default:
return .negative
}
}
}
func printType(_ numbers: [Int]){
for i in numbers{
switch i.kind {
case .negative:
print("- ",terminator:"")
case .positive:
print("+ ",terminator:"")
case .zero:
print("0 ",terminator:"")
}
}
}
printType([-2,51,0,542,-4])
