如何在Swift中使用XMLParser解析本地XML文件？

<?xml version="1.0" encoding="UTF-8"?>
<catalog>
    <book id="bk101">
        <author>Gambardella, Matthew</author>
        <title>XML Developer's Guide</title>
        <genre>Computer</genre>
        <price>44.95</price>
        <publish_date>2000-10-01</publish_date>
        <description>An in-depth look at creating applications with XML.</description>
    </book>
    <book id="bk102">
        <author>Corets, Eva</author>
        <title>Maeve Ascendant</title>
        <genre>Fantasy</genre>
        <price>5.95</price>
        <publish_date>2000-09-03</publish_date>
        <description>A novel about a young woman's journey to save her people.</description>
    </book>
</catalog>

import Foundation

// 定义一个结构体来存储解析后的书籍数据
struct Book {
    var id: String?
    var author: String?
    var title: String?
    var genre: String?
    var price: String?
    var publishDate: String?
    var description: String?
}

// 解析器类，遵循 XMLParserDelegate
class XMLBookParser: NSObject, XMLParserDelegate {
    var books: [Book] = []
    private var currentBook: Book?
    private var currentElement: String = ""
    private var foundCharacters: String = ""

    func parse(xmlFileName: String) -> [Book]? {
        guard let path = Bundle.main.path(forResource: xmlFileName, ofType: "xml"),
              let data = FileManager.default.contents(atPath: path) else {
            print("Error: XML file not found or could not be read.")
            return nil
        }

        let parser = XMLParser(data: data)
        parser.delegate = self

        // 开始解析
        let success = parser.parse()
        if !success {
            print("Parsing failed. Error: \(parser.parserError?.localizedDescription ?? "Unknown error")")
            return nil
        }
        return books
    }

    // MARK: - XMLParserDelegate Methods

    func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String] = [:]) {
        currentElement = elementName
        foundCharacters = "" // 每次遇到新元素，清空之前收集的字符

        if elementName == "book" {
            currentBook = Book()
            currentBook?.id = attributeDict["id"]
        }
    }

    func parser(_ parser: XMLParser, foundCharacters string: String) {
        // 收集当前元素内的字符数据
        // 注意：foundCharacters可能会被多次调用，需要拼接
        foundCharacters += string.trimmingCharacters(in: .whitespacesAndNewlines)
    }

    func parser(_ parser: XMLParser, didEndElement elementName: String, namespaceURI: String?, qualifiedName qName: String?) {
        // 当元素结束时，将收集到的数据赋值给当前书籍对象
        switch elementName {
        case "author":
            currentBook?.author = foundCharacters
        case "title":
            currentBook?.title = foundCharacters
        case "genre":
            currentBook?.genre = foundCharacters
        case "price":
            currentBook?.price = foundCharacters
        case "publish_date":
            currentBook?.publishDate = foundCharacters
        case "description":
            currentBook?.description = foundCharacters
        case "book":
            if let book = currentBook {
                books.append(book)
            }
            currentBook = nil // 清空当前书籍，准备解析下一本
        default:
            break
        }
    }

    func parser(_ parser: XMLParser, parseErrorOccurred parseError: Error) {
        print("Parsing error: \(parseError.localizedDescription)")
    }
}

// 如何使用
// let parser = XMLBookParser()
// if let parsedBooks = parser.parse(xmlFileName: "books") {
//     for book in parsedBooks {
//         print("Book ID: \(book.id ?? "N/A"), Title: \(book.title ?? "N/A"), Author: \(book.author ?? "N/A")")
//     }
// }

// 这是上面解决方案中已经包含的结构体
struct Book {
    var id: String?
    var author: String?
    var title: String?
    var genre: String?
    var price: String?
    var publishDate: String?
    var description: String?
}

// 在 XMLBookParser 类中，我们定义了一个数组来存储解析后的所有书籍
class XMLBookParser: NSObject, XMLParserDelegate {
    var books: [Book] = [] // 存储所有解析完成的Book对象
    private var currentBook: Book? // 临时变量，用于构建当前正在解析的Book对象
    // ... 其他属性和方法 ...
}