Working with XML in Swift: Parsing, Creating, and Processing Data (iOS/macOS)

Working with XML in Swift (iOS/macOS): From Parsing to Creation

XML (eXtensible Markup Language) continues to be used in legacy systems, web services (SOAP, RSS), and configuration files. In Swift for iOS/macOS, there is no built-in library with syntactic sugar, but there is a powerful XMLParser (SAX parser), as well as the popular third-party library AEXML (DOM approach). In this article, we will cover both approaches.

1. Built-in XMLParser (SAX Approach)

XMLParser is an event-driven (SAX) parser from Foundation. It does not load the entire document into memory but calls delegate methods when encountering elements. Ideal for large files.

Example: Parsing an RSS Feed

import Foundation

class RSSParser: NSObject, XMLParserDelegate {    private var currentElement = ""    private var currentTitle = ""    private var items: [String] = []

    func parse(data: Data) -> [String] {        let parser = XMLParser(data: data)        parser.delegate = self        parser.parse()        return items    }

    // MARK: - XMLParserDelegate    func parser(_ parser: XMLParser, didStartElement elementName: String,                namespaceURI: String?, qualifiedName qName: String?,                attributes attributeDict: [String : String] = [:]) {        currentElement = elementName        if elementName == "item" {            currentTitle = ""        }    }

    func parser(_ parser: XMLParser, foundCharacters string: String) {        if currentElement == "title" {            currentTitle += string        }    }

    func parser(_ parser: XMLParser, didEndElement elementName: String,                namespaceURI: String?, qualifiedName qName: String?) {        if elementName == "title" && !currentTitle.isEmpty {            items.append(currentTitle.trimmingCharacters(in: .whitespacesAndNewlines))        }    }}

// Usagelet xmlString = """<rss>  <channel>    <item><title>Swift 6.0</title></item>    <item><title>New Xcode Features</title></item>  </channel></rss>"""if let data = xmlString.data(using: .utf8) {    let parser = RSSParser()    let titles = parser.parse(data: data)    print(titles) // ["Swift 6.0", "New Xcode Features"]}

Important: foundCharacters may be called multiple times for a single text node (especially with Cyrillic characters). Always accumulate the string, do not assign it.

2. AEXML — Convenient DOM Library

AEXML is a lightweight library for working with XML in a DOM style. It allows reading and creating XML without manual event management. It can be installed via Swift Package Manager or CocoaPods.

Installation via Swift Package Manager

Add it to Package.swift or via Xcode: File → Add Packages → enter URL: https://github.com/tadija/AEXML.git

Example: Reading XML

import AEXML

func parseWithAEXML(xmlString: String) -> [String: String]? {    do {        let xmlDoc = try AEXMLDocument(xml: xmlString)        let root = xmlDoc.root

        // Get element value        let name = root["user"]["name"].value ?? ""        let age = root["user"]["age"].value ?? ""

        // Access by attribute        let id = root["user"].attributes["id"] ?? ""

        return ["id": id, "name": name, "age": age]    } catch {        print("Parsing error: \\(error)")        return nil    }}

// Example XMLlet xmlData = """<root>  <user id="42">    <name>Ivan Petrov</name>    <age>30</age>  </user></root>"""if let result = parseWithAEXML(xmlString: xmlData) {    print(result) // ["id": "42", "name": "I