swift学习笔记之--类的计算属性

class Calcuator{
    var a:Int = 1;
    var b:Int = 1;
 
    var sum:Int{
        get{
            return a + b
        }
        set(val){
            b = val - a
        }
    }
}
let cal = Calcuator();
print(cal.sum) //2
cal.sum = 5
print(cal.b) //4

class Calcuator{
    var a:Int = 1;
    var b:Int = 1;
 
    var sum:Int{
        get{
            return a + b
        }
        set{
            b = newValue - a
        }
    }
}

class Calcuator{
    var a:Int = 1;
    var b:Int = 1;
 
    var sum:Int{
        return a + b
    }
}