Swift下标

还记得字典吗？

var numberOfLegs= ["spider": 8,"ant": 6, "cat":4]
numberOfLegs["bird"]= 2

["bird"]就是下标 下标可以在类和结构体中定义。

定义下标

subscript(index: Int) -> Int {
get {
//return anappropriate subscript value here
}
set(newValue) {
// perform a suitable settingaction here
}
}

只读下标

subscript(index: Int) -> Int {
 
//return anappropriate subscript value here
 
}
 

实例：

struct TimesTable {
   let multiplier: Int
    subscript(index: Int) ->Int {
         return multiplier * index
      }
 }
 let threeTimesTable = TimesTable(multiplier: 3)
 println("sixtimes three is \(threeTimesTable[6])")
// prints"six times three is 18"

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