编辑代码

class Sample{
    lazy var no = Number()
    static var minValue : Double = 1.0
    var new_minValue : Double = 0 {
        didSet{
            if new_minValue != Sample.minValue{
                Sample.minValue = new_minValue
            }
        }
    }
    var length : Double = 30.0{
        didSet{

            if length < Sample.minValue {
                length = Sample.minValue
            }
            print("更新后的长为: \(length)")
        }
    }
    var breadth : Double = 15.0{
        didSet{
            if breadth < Sample.minValue{
                breadth = Sample.minValue
            }
        
            print("更新后的宽为: \(breadth)")
        }
    }
    var area : Double{
        get{
            return length*breadth
        }
    }
    
}

class Number{
    var number :Int = 2020967018
}


var temp = Sample()
temp.new_minValue = 10
temp.length = 50
temp.breadth = 5
print("学号为：\(temp.no.number)，面积为：\(temp.area)")