Swift: how to change a property's value without calling its didSet function

Question

How can you set a property\'s value in Swift, without calling its didSet() function outside of an initialization context? The code below was a failed experimen

Answer 1

The issue I was trying to solve is I wanted to get a doCommonUpdate call when one value changed, or one if both changed at the same time. Doing this created a recursion because if either value changed it would call didSet each time. Example setup, mine was more involved:

class Person {
    var first: String = "" {
        didSet {
            updateValues(first: first, last: last)
        }
    }
    var last: String = "" {
        didSet {
            updateValues(first: first, last: last)
        }
    }
    init() {}
    init(first: String, last: String) {
        self.first = first
        self.last = last
    }
    // also want to set both at the same time.
    func updateValues(first: String, last: String) {
//        self.first = first // causes recursion.
//        self.last = last
        doCommonSetup(first: first, last: last)
    }
    func doCommonSetup(first: String, last: String) {
        print(first, last)
    }
}
let l = Person()
l.first = "Betty"
l.last = "Rubble"
_ = Person(first: "Wilma", last: "Flintstone")

> Betty 
> Betty Rubble

Note Wilma does not print because of the commented out lines.

My solution was to move all those variables into a separate struct. The this approach solves the problem and has the side benefit of creating a another grouping which helps meaning. We still get the doCommonSetup when either value changes independently and when we get both values changed at the same time.

class Person2 {
    struct Name {
        let first: String
        let last: String
    }
    var name: Name
    init() {
        name = Name(first: "", last: "")
    }
    init(first: String, last: String) {
        name = Name(first: first, last: last)
        updateValues(name: name)
    }
    var first: String = "" {
        didSet {
            name = Name(first: first, last: self.last)
            updateValues(name: name)
        }
    }
    var last: String = "" {
        didSet {
            name = Name(first: self.first, last: last)
            updateValues(name: name)
        }
    }
    // also want to set both at the same time.
    func updateValues(name: Name) {
        self.name = name
        doCommonSetup(name: name)
    }
    func doCommonSetup(name: Name) {
        print(name.first, name.last)
    }
}

let p = Person2()
p.first = "Barney"
p.last = "Rubble"
_ = Person2(first: "Fred", last: "Flintstone")

> Barney 
> Barney Rubble
> Fred Flintstone