Deep copy of array with elements containing an array? - swift

Question

I'm trying to make a deep copy of a list of the following objects:
struct Book {
var title: String
var author: String
var pages: Int
}
struct BookShelf {
var number: Int
}
class BookShelfViewModel {
var bookShelf: BookShelf
var number: Int
var books: [BookViewModel]?
init(bookShelf: BookShelf) {
self.bookShelf = bookShelf
self.number = bookShelf.number
}
required init(original: BookShelfViewModel) {
self.bookShelf = original.bookShelf
self.number = original.number
}
}
class BookViewModel {
var book: Book
var title: String
var author: String
var pages: Int
init(book: Book) {
self.book = book
self.title = book.title
self.author = book.author
self.pages = book.pages
}
required init(original: BookViewModel) {
self.book = original.book
self.title = original.title
self.author = original.author
self.pages = original.pages
}
}
Books for BookShelf is fetched in the BookShelfViewModel.
If I go like:
var copiedArray = originalArray
for bs in copiedArray {
bs.books = bs.books.filter { $0.title == "SampleTitle" }
}
The above filter both the copiedArray and the originalArray, and I obviously just want the copiedArray altered.
When I clone the array like this:
var originalArray = [BookShelfViewModel]()
... // Fill the array
var clonedArray = originalArray.clone()
clonedArray is cloned, but clonedArray.books is empty.
I've created the extension and followed this gist. How do I clone the array in the objects in the array?
I've done a quick playground to visualize the problem, hopefully it helps understand what I'm talking about.

Answer 1

In your copying initialiser in BookShelfViewModel you don't actually clone the books array. You need to add self.books = original.books?.clone() to required init(original: BookShelfViewModel)
class BookShelfViewModel: Copying {
var bookShelf: BookShelf
var number: Int
var books: [BookViewModel]?
init(bookShelf: BookShelf) {
self.bookShelf = bookShelf
self.number = bookShelf.number
}
required init(original: BookShelfViewModel) {
self.bookShelf = original.bookShelf
self.books = original.books?.clone()
self.number = original.number
}
}