Swift extension #1 기존 자료형의 확장

1. extension - 기존 자료형의 확장
2. 

3. 예

4. extension Double {
5. var km: Double { return self * 1_000.0 }
6. var m: Double { return self }
7. var cm: Double { return self / 100.0 }
8. var mm: Double { return self / 1_000.0 }
9. var ft: Double { return self / 3.28084 }
10. }
11. let oneInch = 25.4.mm
12. print("One inch is \(oneInch) meters")
13. // prints "One inch is 0.0254 meters"
14. let threeFeet = 3.ft
15. print("Three feet is \(threeFeet) meters")
16. // prints "Three feet is 0.914399970739201 meters"

1. let aMarathon = 42.km + 195.m
2. print("A marathon is \(aMarathon) meters long")
3. // prints "A marathon is 42195.0 meters long"