var circumName: String?
var circumNumber: String?
var circumarea: String?
func buildingIdentifier() -> String? {
if circumName != nil {
return circumName
} else if circumNumber != nil {
return circumNumber
} else {
return nil
}
}
}
let circname = rectangle()
circname.print?[0] = radius(radiusname: "Diameter")
let printing = circle()
printing.area.append(radius(radiusname: "Units"))
printing.area.append(radius(radiusname: "Meter"))
circname.print = printing
if let radiusName = circname.print?[0].radiusname {
println("Radius is measured in (radiusName).")
} else {
println("Radius is not specified.")
}
当我们使用 playground 运行上面的程序，得到以下结果。
Radius is measured in Units.
在上面的程序被指定为成员函数 “radiusName” 的实例值。 因此，程序现在调用函数将有返回值。
可选类型访问下标
复制代码class rectangle {
var print: circle?
}
class circle {
var area = [radius]()
var cprint: Int {
return area.count
}
subscript(i: Int) -> radius {
get {
return area[i]
}
set {
area[i] = newValue
}
}
func circleprint() {
println("The number of rooms is (cprint)")
}
var rectarea: circumference?
}
class radius {
let radiusname: String
