解析soap响应（iphone/touchxml）时出现问题

我创建了一个Web服务，它可以工作，问题在于Web服务的响应。 我有这个xml（我想用touchxml解析），问题是touchxml发现了两个xml，一个在另一个内部，它会崩溃。 我的问题是，如何解析这个xml？如何删除所有的东西，比如soap-env、xmlns

<?xml version="1.0" encoding="ISO-8859-1"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"><SOAP-ENV:Body>
<ns1:getCategoriesResponse xmlns:ns1="http://192.168.1.30/wyws/server.php"><return xsi:type="xsd:string">

    <?xml version="1.0" encoding="UTF-8"?>
    <categories>
       <category id="1" desc="Encontrar Códigos " icon="wy">Código </category>
       <category id="3" desc="" icon="farm">Far</category>
       <category id="5" desc="" icon="gas">Gas</category>
       <category id="6" desc="" icon="hos">Hos</category>
       <category id="7" desc="" icon="pol">Pol</category>
    </categories>

</return></ns1:getCategoriesResponse></SOAP-ENV:Body></SOAP-ENV:Envelope>

然后

-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{

    NSLog(@"DONE. Received Bytes: %d", [webData length]);

    NSString *theXML = [[NSString alloc] initWithBytes: [webData mutableBytes] length:[webData length] encoding:NSISOLatin1StringEncoding];


NSLog(theXml);
....
}

---

我写了这个，它不是很优雅，但它很有效

 NSRange in = [tmpTheXml rangeOfString:@"<return xsi:type=\"xsd:string\">"];
 NSRange fi = [tmpTheXml rangeOfString:@"</return>"];
 int inic = in.location + in.length;
 NSRange tmprange = {inic,fi.location - inic} ;
 tmpTheXml = [tmpTheXml substringWithRange:tmprange];

NSRange in=[tmpTheXml rangeOfString:@”“；
NSRange fi=[tmpTheXml rangeOfString:@”“；
int inic=英寸位置+英寸长度；
NSRange tmprange={inic，fi.location-inic}；
tmpTheXml=[tmpTheXml substringWithRange:tmprange]；

 NSRange in = [tmpTheXml rangeOfString:@"<return xsi:type=\"xsd:string\">"];
 NSRange fi = [tmpTheXml rangeOfString:@"</return>"];
 int inic = in.location + in.length;
 NSRange tmprange = {inic,fi.location - inic} ;
 tmpTheXml = [tmpTheXml substringWithRange:tmprange];