如何从XML中提取链接href？

问：

我正在为我的应用程序使用AEXML，每当我尝试从xml数据中提取链接时，我都会遇到麻烦。

下面是 XML 数据：

<entry>
    <updated>2015-08-06T01:17:16-07:00</updated>
    <id im:id="969299396">https://itunes.apple.com/us/album/love-and-marriage/id969298500?i=969299396&uo=2</id>
    <title>Love and Marriage - Frank Sinatra</title>
    <im:name>Love and Marriage</im:name>
    <link rel="alternate" type="text/html" href="https://itunes.apple.com/us/album/love-and-marriage/id969298500?i=969299396&uo=2" />
    <im:contentType label="Music" term="Music">
        <im:contentType label="Track" term="Track" />
    </im:contentType>
    <category term="Easy Listening" label="Easy Listening" im:id="25" scheme="https://itunes.apple.com/us/genre/music-easy-listening/id25?uo=2" />
    <link href="http://a1901.phobos.apple.com/us/r1000/020/Music5/v4/c1/9c/ed/c19ced58-1bd8-4940-7edd-a3c540be7584/mzaf_5226977055945471954.plus.aac.p.m4a" title="Preview" rel="enclosure" type="audio/x-m4a" im:assetType="preview">
        <im:duration>30000</im:duration>
    </link>
    <im:artist href="https://itunes.apple.com/us/artist/frank-sinatra/id171366?uo=2">Frank Sinatra</im:artist>
    <im:price amount="1.29000" currency="USD">$1.29</im:price>
    <im:image height="55">http://is5.mzstatic.com/image/pf/us/r30/Music3/v4/48/8c/6c/488c6cd9-f2e2-fb72-a1d9-f8e0a6cbce63/UMG_cvrart_00602547253309_01_RGB72_1500x1500_15UMGIM08561.55x55-70.jpg</im:image>
    <im:image height="60">http://is2.mzstatic.com/image/pf/us/r30/Music3/v4/48/8c/6c/488c6cd9-f2e2-fb72-a1d9-f8e0a6cbce63/UMG_cvrart_00602547253309_01_RGB72_1500x1500_15UMGIM08561.60x60-50.jpg</im:image>
    <im:image height="170">http://is1.mzstatic.com/image/pf/us/r30/Music3/v4/48/8c/6c/488c6cd9-f2e2-fb72-a1d9-f8e0a6cbce63/UMG_cvrart_00602547253309_01_RGB72_1500x1500_15UMGIM08561.170x170-75.jpg</im:image>
    <rights>℗ 2015 Universal Music Enterprises</rights>
    <im:releaseDate label="April 21, 2015">2015-04-21T00:00:00-07:00</im:releaseDate>
    <im:collection>
        <im:name>Ultimate Sinatra</im:name>
        <link rel="alternate" type="text/html" href="https://itunes.apple.com/us/album/ultimate-sinatra/id969298500?uo=2" />
        <im:contentType label="Music" term="Music">
            <im:contentType label="Album" term="Album" />
        </im:contentType>
    </im:collection>
    <content type="html"><table border="0" width="100%">
<tr>
    <td>
        <table border="0" width="100%" cellspacing="0" cellpadding="0">
            <tr valign="top" align="left">

                    <td align="center" width="166" valign="top">
                        <a href="https://itunes.apple.com/us/album/love-and-marriage/id969298500?i=969299396&uo=2"><img border="0" alt="Frank Sinatra - Love and Marriage  artwork" src="http://is1.mzstatic.com/image/pf/us/r30/Music3/v4/48/8c/6c/488c6cd9-f2e2-fb72-a1d9-f8e0a6cbce63/UMG_cvrart_00602547253309_01_RGB72_1500x1500_15UMGIM08561.170x170-75.jpg" /></a>
                    </td>
                    <td width="10"><img alt="" width="10" height="1" src="https://s.mzstatic.com/images/spacer.gif" /></td>
                    <td width="95%">


                    <b><a href="https://itunes.apple.com/us/album/love-and-marriage/id969298500?i=969299396&uo=2">Love and Marriage</a></b><br/>




                        <a href="https://itunes.apple.com/us/album/ultimate-sinatra/id969298500?uo=2">Ultimate Sinatra</a><br/>


                    <a href="https://itunes.apple.com/us/artist/frank-sinatra/id171366?uo=2">Frank Sinatra</a>

                   <font size="2" face="Helvetica,Arial,Geneva,Swiss,SunSans-Regular">

                        <br/>
                        <b>Genre:</b> <a href="https://itunes.apple.com/us/genre/music-easy-listening/id25?uo=2">Easy Listening</a>

                        <br/>
                        <b>Price:</b> $1.29

                        <br/>
                        <b>Release Date:</b> April 21, 2015

                    </font>
                </td>
            </tr>
        </table>
    </td>
</tr>
<tr>
    <td>



            <font size="2" face="Helvetica,Arial,Geneva,Swiss,SunSans-Regular"> &#169; ℗ 2015 Universal Music Enterprises</font>

    </td>
</tr>

这是我尝试过的代码：

var error: NSError?
    var data : NSData = NSData(contentsOfURL: NSURL(string: "https://itunes.apple.com/us/rss/topsongs/limit=10/genre=25/xml")!)!
    if let xmlDoc = AEXMLDocument(xmlData: data, error: &error) {
        println(xmlDoc.xmlString)
        println("rene 2")
        if let cats = xmlDoc.root["entry"].all {
            println(cats)
            println("rene 3")
            for cat in cats {

                println("rene 4")
                var title = cat["title"].value
                var artist = cat["artist"].value
                var albumUrl = cat["im:image"].value
                var tes = cat.attributes["link"]!.stringValue

                println(">>>>>\(tes)<<<<<<")


            }
        }

    }

我打印标题、艺术家等没有问题。但是当我尝试获取/提取链接 href 时，我总是失败。

请给我一个建议。