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} 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.") } When we run the above program using playground, we get the following result: Radius is measured in Units. In the above program, the instance values for the membership function 'radiusName' is specified. Hence program call to the function will now return values.

Accessing Subscripts of Optional Type class rectangle { var print: circle? }

class circle { var area = [radius]() var cprint: Int { 172

Swift is a powerful and instinctive programming language for macOS, iOS, watchOS and tvOS....