从零开始自学Swift(七)

类与结构体的计算属性

/*定义一个点*/struct Point {    var x:Double!,y:Double!}/*定义矩形的宽高*/struct Size {    var width:Double!,height:Double!}/*定义一个矩形*/struct Rect {    var origin=Point()    var size=Size()    var center:Point{        get{            let centerX=origin.x+(size.width/2)            let centerY=origin.y+(size.height/2)            return Point(x: centerX, y: centerY)        }        set(newCenter){            origin.x=newCenter.x-(size.width/2)            origin.y=newCenter.y-(size.height/2)        }    }}var rectangular=Rect(origin: Point(x: 0, y:0), size: Size(width: 2, height: 2))print(rectangular.center)

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下标脚本

关键词subscript

/*下标脚本*/struct TimeTable {    let multiplier:Int    subscript (index:Int)->Int{        return multiplier*index    }}let fourTimeTable=TimeTable(multiplier: 4)print(fourTimeTable[8])//32