Mutable Reference Type in Struct

MutableReferenceTypeInStruct.swift

import Foundation

class ProductFactory: NSObject, NSCopying {
    var items = 8

    func copy(with zone: NSZone? = nil) -> Any {
        let factory = ProductFactory()
        factory.items = items
        return factory
    }
}

struct Product {
    let identifier: Int
    let name: String
    private var _factory = ProductFactory()

    init(identifier: Int, name: String) {
        self.identifier = identifier
        self.name = name
    }

    var getFactory: ProductFactory {
        return _factory
    }

    var setFactory: ProductFactory {
        mutating get {
            if !isKnownUniquelyReferenced(&factory) {
                _factory = factory.copy() as! ProductFactory
            }
            return _factory
        }

    }
}


let productA = Product(identifier: 234, name: "electronics")

var productB = productA

productB.setFactory.items = 4

print("product A items \(productA.getFactory.items)")
print("product B items \(productB.getFactory.items)")