iOS Swift - Reference between Objects - ios

Question

I have a shared handler class in which I 'manage' objects.
In this shared class, there is a 'main object (mainObject)' and a 'single object (singleData)'.
If I now assign the singleData with the reference to mainObject.data[index] in viewA and then change mainObject.data[index] in viewB, then the singleData object also changes. How can I avoid this strong-reference here?
==> In short: I want to change the mainObject without changing the singleObject. <==
struct kOBJECT {
let name: String
let data: [Int]
}
class HandlerClass {
let shared = HandlerClass()
var mainObject = kOBJECT(name: "AnyName", data: [1,2,3,4,5])
var singleData: Int?
}
class viewA: UIViewController {
.....
func didSelectRow(at indexPath: IndexPath) {
HandlerClass.shared.singleData = HandlerClass.shared.mainObject.data[indexPath.row] // Create Reference
viewB.indexPath = indexPath
pushToViewController(viewB)
}
}
class viewB: UIViewController {
.....
public var indexPath: IndexPath!
func someFunction() {
HandlerClass.shared.mainObject.data[indexPath.row] = 10000 // <- Does this also change the `singleData` Reference? In my case it does......
}
}
I tried the following in 'didSelectRow'
let tempValue = HandlerClass.shared.mainObject.data[indexPath.row]
HandlerClass.shared.singleObject = tempValue

Answer 1

You misunderstand reference meaning. Reference works only of instances - that's a part of memory reserved for specific objects. Structs are also objects, but it works as Type (similar to Int, String, Double, Float, etc), so when you modify a struct as a result you will have a new object, but for class instance, you will still modify the same object as you copied only reference to that object.
Here example below:
class Apple {
init(name: String) {
self.name = name
}
var name: String
}
struct Pear {
var name: String
}
var apple = Apple(name: "Apple 1")
var pear = Pear(name: "Pear 1")
var apple2 = apple // here we copy only reference
apple2.name = "Apple 2"
print(apple.name) // 1st object
print(apple2.name) // the same object
var pear2 = pear // here we create new object
pear2.name = "Pear 2"
print(pear.name) // 1st object
print(pear2.name) // 2nd object
Also a result (run on Playground)