Question

所以我刚刚将我的swift更新为2.0，显然我的代码中出现了一些错误。那就是我现在所拥有的。

unc loadRssFeed(data: NSURL) {

    var myRssParser : ParserManager = ParserManager.alloc().initWithURL(data) as! ParserManager

    myRssFeed = myRssParser.feeds

    tableView.reloadData()
}

Fixit建议将'var'更改为'let'并使用object initializer而不是alloc（）。但问题是我以前从未使用它（授予我的Swift经验就像四周）。

我应该遵循fixit指令吗？我如何解决alloc（）问题。

谢谢！

更新了机智解析器代码：

class ParserManager: NSObject, NSXMLParserDelegate {

var parser = NSXMLParser()
var feeds = NSMutableArray()
var elements = NSMutableDictionary()
var element = NSString()
var ftitle = NSMutableString()
var link = NSMutableString()
var fdescription = NSMutableString()
var fdate = NSMutableString()


func initWithURL(url :NSURL) -> AnyObject {
    startParse(url)
    return self
}
func startParse(url :NSURL) {
    feeds = []
    parser = NSXMLParser(contentsOfURL: url)!
    parser.delegate = self
    parser.shouldProcessNamespaces = false
    parser.shouldReportNamespacePrefixes = false
    parser.shouldResolveExternalEntities = false
    parser.parse()
}

func allFeeds() -> NSMutableArray {
    return feeds
}
func parser(parser: NSXMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {

    self.element = elementName

    if self.element == "item" {

        self.ftitle = ""
        self.fdescription = ""

        self.fdate = ""

    }
}
func parser(parser: NSXMLParser, didEndElement elementName: String, namespaceURI: String?, qualifiedName qName: String?) {

    if (elementName as NSString).isEqualToString("item") {
        if ftitle != "" {
            elements.setObject(ftitle, forKey: "title")
        }



        if fdescription != "" {
            elements.setObject(fdescription, forKey: "description")
        }

        if fdate != "" {
            elements.setObject(fdate, forKey: "pubDate")
        }

        feeds.addObject(elements)
    }

}
func parser(parser: NSXMLParser, foundCharacters string: String?) {

    if element.isEqualToString("title") {
        ftitle.appendString(string!)

    }else if element.isEqualToString("description") {
        fdescription.appendString(string!)
    }else if element.isEqualToString("pubDate") {
        fdate.appendString(string!)
    }
}


}

Answer 1

修复应该如下所示：

let myRssParser = ParserManager(URL: data) as! ParserManager

或者可能是这样，取决于ParserManager的编写方式：

let myRssParser = ParserManager(url: data) as! ParserManager

甚至有可能您不必使用参数名称：

let myRssParser = ParserManager(data) as! ParserManager

Answer 2

如上所述，您不应直接调用alloc和init...方法。此外，ParserManager类不应使用initWithURL方法，而应采用init类URL参数。现有代码似乎遵循Objective-C模式，但Swift有自己的约定。

但更广泛地说，我建议不要执行同步网络请求，当您拨打NSXMLParser(contentsOfURL:)时，会发生什么事情。最好异步请求数据，然后重构代码以遵循异步模式（例如completionHandler闭包）。例如：

class ParserManager: NSObject, NSXMLParserDelegate {

    /// The NSMutableArray used internally by this class

    private var feeds = NSMutableArray()

    /// Initiate parsing asynchronously; note, I'm returning the `NSURLSessionTask` in case you want to cancel it at some later point

    func parse(URL: NSURL, completionHandler: (NSMutableArray?, NSError?)->()) -> NSURLSessionTask {
        let task = NSURLSession.sharedSession().dataTaskWithURL(URL) { data, response, error in
            guard data != nil else {
                dispatch_async(dispatch_get_main_queue()) {
                    completionHandler(nil, error)
                }
                return
            }

            let parser = NSXMLParser(data: data!)
            parser.delegate = self

            if parser.parse() {
                dispatch_async(dispatch_get_main_queue()) {
                    completionHandler(self.feeds, nil)
                }
            } else {
                dispatch_async(dispatch_get_main_queue()) {
                    completionHandler(nil, parser.parserError)
                }
            }
        }
        task.resume()

        return task
    }

    // NSXMLParserDelegate methods implemented here

}

然后，您可以使用完成处理程序语法来指定在网络请求和解析完成时您要执行的操作：

let URL = NSURL(string: "...")
let myRssParser = ParserManager()
myRssParser.parse(URL) { feeds, error in
    guard feeds != nil else {
        print(error)
        return
    }

    // use `feeds` here, e.g.

    self.feeds = feeds            // update your local property
    self.tableView.reloadData()   // and reload the table
}

// but don't use `feeds` here, since it won't be done by the time we get here

swift中的alloc（）错误

2 个答案: