使用属性观察器进行属性封装-Swift

Question

I am trying to do property encapsulation with property observer. Refer below Sample Code. If userName is empty then need to set username as Unknown . I am checking this condition in willSet but unfortunately it unable to set the value as self.userName = "Unknown" .

If I do same with getter-setter then it can be achievable with extra private param. Check Below code.

With get-set

private var userName : String
var name : String {
    get {
        return self.userName
    }

    set {
        if newValue.isEmpty {
            self.userName = "Unknown"
        }
    }
}

Sample Code - WillSet

class MyClass {
    var userName : String {
        willSet{
            print("Will set called")
            if newValue.isEmpty {
                print("If condi \(newValue) ..")
                self.userName = "Unknown"
            }
        }

        didSet {
            print("Did set called")
        }
    }
    init(name : String) {

        self.userName = name

    }
}


let c = MyClass(name: "Hello")
c.userName = ""
print("var ->", c.userName)

Output:

Q: How to achieve this encapsulation with willSet?? If I somewhere misconcepted then please correct me.

Thanks

Answer 1

Just reset in didSet :

class MyClass {
    var userName : String {
        didSet {
            if userName.isEmpty {
                self.userName = "Unknown"
            }
        }
    }

    init(name : String) {
        self.userName = name
    }
}

But keep in mind that property observers are not called from init so if someone does let c = MyClass(name: "") then userName will still be the empty string.