}
var rectarea: circumference?
}
class radius {
let radiusname: String
init(radiusname: String) { self.radiusname = radiusname }
}
class circumference {
var circumName: String?
var circumNumber: String?
var street: String?
func buildingIdentifier() -> String? {
if circumName != nil {
return circumName
} else if circumNumber != nil {
return circumNumber
} else {
return nil
}
}
}
let rectname = rectangle()
if let rectarea = rectname.print?.cprint {
println("Area of rectangle is (rectarea)")
} else {
println("Rectangle Area is not specified")
}
当我们使用 playground 运行上面的程序，得到以下结果。
Rectangle Area is not specified
通过可选链调用方法
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("Area of Circle is: (cprint)")
}
var rectarea: circumference?
}
class radius {
let radiusname: String
init(radiusname: String) { self.radiusname = radiusname }
}
class circumference {
var circumName: String?
var circumNumber: String?
