Explaining how to work with XML in iOS with Swift 4.2

Book.swift

class Book {
    var bookTitle: String = String()
    var bookAuthor: String = String()
}

books.xml

<?xml version="1.0"?>
<catalog>
    <book>
        <title>To Kill a Mockingbird</title>
        <author>Harper Lee</author>
    </book>
    <book>
        <title>1984</title>
        <author>George Orwell</author>
    </book>
    <book>
        <title>The Lord of the Rings</title>
        <author>J.R.R Tolkien</author>
    </book>
    <book>
        <title>The Catcher in the Rye</title>
        <author>J.D. Salinger</author>
    </book>
    <book>
        <title>The Great Gatsby</title>
        <author>F. Scott Fitzgerald</author>
    </book>
</catalog>

ViewController.swift

class ViewController: UIViewController, XMLParserDelegate {

    // MARK:- Varibles
    var books: [Book] = []
    
    // MARK:- Life Cycle
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        if let path = Bundle.main.url(forResource: "books", withExtension: "xml") {
            if let parser = XMLParser(contentsOf: path) {
                parser.delegate = self
                parser.parse()
            }
        }
    }

    // using this variable to hold the element name in order to know which element I'm currently working on
    var currentElementName: String = String()
    // using a variable for each model or value I'm going to parse it so I can add it later to an array or use it in anyway I may see fit
    var currentBook: Book = Book()
    
    // MARK:- XMLParserDelegate
    func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String] = [:]) {
        self.currentElementName = elementName
    }
    
    /// after finish reading the tag insert the created model in the array (this is just an example)
    func parser(_ parser: XMLParser, didEndElement elementName: String, namespaceURI: String?, qualifiedName qName: String?) {
        if elementName == "book" {
            self.books.append(self.currentBook)
            self.currentBook = Book()
        }
    }
    
    /// reading tag value
    func parser(_ parser: XMLParser, foundCharacters string: String) {
        // removing new lines and un-intended white spaces
        let data = string.trimmingCharacters(in: .whitespacesAndNewlines)
        // in case empty don't do anything
        // otherwise insert the data to the correct location
        if (!data.isEmpty) {
            if self.currentElementName == "title" {
                self.currentBook.bookTitle += data
            } else if self.currentElementName == "author" {
                self.currentBook.bookAuthor += data
            }
        }
    }
}