将方法外包给静态方法时出现 Swift 错误

Question

我想开始使用 Swift 编写我的 Android 应用程序。应用程序应使用 url 中的 xml 来显示对象列表。

UITableViewController 中的解析和显示已经开始工作。现在我想将解析外包到一个静态类中，每当我想要获取对象列表时都可以使用它。

问题是，当我使用外包类时，我收到 EXC_BAD_ACCESS 错误。我认为问题可能是，我正在尝试访问已释放的内存，但我不确定。

下面您可以找到我正在使用的代码:

XML(简化):

<result>
     <row>
         <id>1</id>
         <name>Alpha</name>
    </row>
    <row>
        <id>2</id>
        <name>Beta</name> 
    </row>
    <row>
        <id>3</id>
        <name>Gamma</name>
    </row>
</result>

XMLHelper.swift(外包类，使用外包类ToolXMLParserDelegate.swift):

import Foundation

class XMLHelper : NSObject{

     static var baseURL = "{myServerUrl}" // not public for security reasons
     static var toolListString = "getToolList.php"

     class func getToolList() -> [Tool]? {
         var toolList: [Tool] = []

         let url = baseURL+toolListString

         guard let myURL = URL(string: url) else {
             print("URL not defined properly")
             return nil
         }
         guard let parser = XMLParser(contentsOf: myURL as URL) else {
             print("Cannot Read Data")
             return nil
         }

         parser.delegate = ToolXMLParserDelegate(toolList: &toolList)

         if !parser.parse() { //HERE I GET THE ERROR
             print("Data Errors Exist:")
             let error = parser.parserError!
             print("Error Description:\(error.localizedDescription)")
             //print("Error reason:\(error.localizedFailureReason)")
             print("Line number: \(parser.lineNumber)")
         }

         return toolList
     }
 }

ToolXMLParserDelegate.swift:

import Foundation

class ToolXMLParserDelegate : NSObject, XMLParserDelegate {

    var tools: [Tool] = []
    var eName: String = String()
    var toolId = String()
    var toolName = String()

    init(toolList : inout [Tool]) {
        self.tools = toolList
    }


    func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {
        eName = elementName
        if elementName == "row" {
            toolId = String()
            toolName = String()
        }
    }


    func parser(_ parser: XMLParser, didEndElement elementName: String, namespaceURI: String?, qualifiedName qName: String?) {
        if elementName == "row" {

            let tool = Tool()
            tool.id = Int(toolId)!
            tool.name = toolName
            tools.append(tool)
        }
    }


    func parser(_ parser: XMLParser, foundCharacters string: String) {
        let data = string.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)

        if (!data.isEmpty) {
            if eName == "id" {
                toolId += data
            } else if eName == "name" {
                toolName += data
            }
        }
    }
}

工具.swift:

import UIKit

class Tool: NSObject {

    var id: Int = Int()
    var name: String = String()

    override init() {}

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

    init(name: String) {
        self.name = name
    }
}

ToolTableViewController.swift:(使用 XMLHelper.getToolList())

import UIKit

class ToolTableViewController: UITableViewController, XMLParserDelegate {

    var tools: [Tool] = []
    var eName: String = String()
    var toolId = String()
    var toolName = String()

   override func viewDidLoad() {
        super.viewDidLoad()

        tableView.tableFooterView = UIView() // to remove empty cells in the list
    }

    override func viewWillAppear(_ animated: Bool) {
        tools = XMLHelper.getToolList()!

        // this code piece is working, but i want to outsource it, so i can use it again
        /*
        let url = "{myUrl}" // not public for security reason
        let myURL = URL(string: url)
        let parser = XMLParser(contentsOf: myURL!)!
        parser.delegate = self as XMLParserDelegate
        parser.parse()
        */

        tableView.reloadData()*/

        print("view did refresh")
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    // MARK: - Table view data source

    override func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return tools.count
    }


    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        //let cell = tableView.dequeueReusableCell(withIdentifier: "reuseIdentifier", for: indexPath)

    let cellIdentifier = "ToolTableViewCell" // simple TableViewCell with a label

    guard let cell = tableView.dequeueReusableCell(withIdentifier: cellIdentifier, for: indexPath) as? ToolTableViewCell  else {
        fatalError("The dequeued cell is not an instance of ToolTableViewCell.")
    }

    let tool = tools[indexPath.row]

    cell.labelName.text = String(tool.id)+"  "+tool.name

    return cell
}

// MARK: XMLParserDelegate (this code here is only used when the code above is uncommented, it is the same as the code in ToolXMLParserDelegate)

    func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {
        eName = elementName
        if elementName == "row" {
            toolId = String()
            toolName = String()
        }
    }

    func parser(_ parser: XMLParser, didEndElement elementName: String, namespaceURI: String?, qualifiedName qName: String?) {
        if elementName == "row" {

            let tool = Tool()
            tool.id = Int(toolId)!
            tool.name = toolName

            tools.append(tool)
        }
    }

    func parser(_ parser: XMLParser, foundCharacters string: String) {
        let data = string.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)

        if (!data.isEmpty) {
            if eName == "id" {
                toolId += data
            } else if eName == "name" {
                toolName += data
            }
        }
    }   
}

Answer 1

我现在可以使用了，看起来我搞乱了引用资料。

这是我所做的更改:

ToolXMLParserDelegate

init(toolList : [Tool]) { //removed inout
    self.tools = toolList
}

XMLHelper

class func getToolList() -> [Tool]? {
    // not needed anymore
    //var toolList: [Tool] = []

    let baseURL = "https://henkel.simonus.de/approval/xml/"
    let toolListString = "getToolList.php"

    let url = baseURL+toolListString

    guard let myURL = URL(string: url) else {
        print("URL not defined properly")
        return nil
    }
    guard let parser = XMLParser(contentsOf: myURL as URL) else {
        print("Cannot Read Data")
        return nil
    }

    // CHANGES
    let myDelegate = ToolXMLParserDelegate(toolList: []) // pass an empty array
    parser.delegate = myDelegate

    if !parser.parse() {
        print("Data Errors Exist:")
        let error = parser.parserError!
        print("Error Description:\(error.localizedDescription)")
        //print("Error reason:\(error.localizedFailureReason)")
        print("Line number: \(parser.lineNumber)")
    }

    // return the list of the delegate instead of the xmlhelpers toolList
    return myDelegate.tools
}