swift语言点评十二-Subscripts

Posted 2020-10-29 zzfx

Classes, structures, and enumerations can define subscripts, which are shortcuts for accessing the member elements of a collection, list, or sequence.

 

下标的形式和函数相同，并且set和get合一

subscript(row: Int, column: Int) -> Double

 

比较：

In addition to simple properties that are stored, properties can have a getter and a setter.

1. class EquilateralTriangle: NamedShape {
2. var sideLength: Double = 0.0
4. init(sideLength: Double, name: String) {
5. self.sideLength = sideLength
6. super.init(name: name)
7. numberOfSides = 3
8. }
10. var perimeter: Double {
11. get {
12. return 3.0 * sideLength
13. }
14. set {
15. sideLength = newValue / 3.0
16. }
17. }
19. override func simpleDescription() -> String {
20. return "An equilateral triangle with sides of length \(sideLength)."
21. }
22. }
23. var triangle = EquilateralTriangle(sideLength: 3.1, name: "a triangle")
24. print(triangle.perimeter)
25. triangle.perimeter = 9.9
26. print(triangle.sideLength)