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Swift

var rectarea: circumference? }

class radius { let radiusname: String init(radiusname: String) { self.radiusname = radiusname } }

class circumference { 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()

if circname.print?.circleprint() != nil { println("Area of circle is specified)") } else { println("Area of circle is not specified") } When we run the above program using playground, we get the following result: Area of circle is not specified The function circleprint() declared inside the circle() sub class is called by creating an instance named 'circname'. The function will return a value if it contains some value 168

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