Swift下标语法

//数组使用下标
var ttArr = ["aa", "b", "c"]
var ta = ttArr[0]

//字典使用下标
var ttDic = ["aa":11, "bb":22, "cc":33]
var td = ttDic["aa"]

struct Ttss {
    let length: Int
    //这是下标的关键字
    subscript(width: Int, height: Int) -> Int {
        return width * height * length;
    }
}

let ss = Ttss(length: 2)
let area = ss[4, 5]
print("获得的面积：\(area)")