iphone - 无法理解 NSXMLParser

Question

我无法理解 NSXMLParser。我尝试了一些外部 XML 解析器，但没有运气。我要做的是解析 GDATA Youtube API xml，它检索视频的 xml。这工作正常，我有 xml，但很难重复元素。我只需要一个可以检索元素的示例，例如 (media:thumbnail url="" )(/media:thumbnail)

如何从元素 media:thumbnail 中获取 url 值

我请求的网址是https://gdata.youtube.com/feeds/api/videos?q=football+-soccer&orderby=published&start-index=11&max-results=10&v=2

Answer 1

这是您可以使用的方式NSXMLParser：

在您的 .h 文件中声明：

NSMutableData       *webPortFolio;
NSMutableString     *soapResultsPortFolio;
NSURLConnection     *conn;

//---xml parsing---

NSXMLParser         *xmlParserPortFolio;
BOOL                elementFoundPortFolio;
NSMutableURLRequest *req;

NSString            *theXMLPortFolio;
NSString            *strSoapMsg;
UIAlertView         *alertView;

在您的 .m 文件中使用以下代码：

-(void)callURL
{

     //Your logic to call URL.

     conn = [[NSURLConnection alloc] initWithRequest:req delegate:self];
     if (conn)
     {
         webPortFolio = [[NSMutableData data] retain];
     }
}

要处理响应，您可以使用以下功能：

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [webPortFolio setLength:0];     
}

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [webPortFolio appendData:data];
}

-(void) connection:(NSURLConnection *) connection didFailWithError:(NSError *) error
{

    NSLog(@"error...................%@",[error description]);
    [webPortFolio release];
    [connection release];
}

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

    //Check the request and returns the response.

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

    theXMLPortFolio = [[NSString alloc] 
                      initWithBytes: [webPortFolio mutableBytes] 
                      length:[webPortFolio length] 
                      encoding:NSUTF8StringEncoding];

    //---shows the XML---

    NSLog(@"shows the XML %@",theXMLPortFolio);
    [theXMLPortFolio release];    

    if(xmlParserPortFolio)
    {
        [xmlParserPortFolio release];
    }
    xmlParserPortFolio = [[NSXMLParser alloc] initWithData: webPortFolio];
    [xmlParserPortFolio setDelegate: self];
    [xmlParserPortFolio setShouldResolveExternalEntities:YES];
    [xmlParserPortFolio parse];
    [webPortFolio release];
    [connection release];
}

//---when the start of an element is found---
-(void)  parser:(NSXMLParser *) parser 
didStartElement:(NSString *) elementName 
   namespaceURI:(NSString *) namespaceURI 
  qualifiedName:(NSString *) qName
     attributes:(NSDictionary *) attributeDict
{

    if( [elementName isEqualToString:@"GetPortfolioListResult"])
    {
        if (!soapResultsPortFolio)
        {
            soapResultsPortFolio = [[NSMutableString alloc] init];
        }
        elementFoundPortFolio = TRUE;
        NSLog(@"Registration...%@",soapResultsPortFolio);
    }
    else if([elementName isEqualToString:@"your_tag_name"])
    {
        elementFoundPortFolio = TRUE;
    }
    else if([elementName isEqualToString:@"your_tag_name"])
    {
        elementFoundPortFolio = TRUE;
    }
    else if([elementName isEqualToString:@"your_tag_name"])
    {
        elementFoundPortFolio = TRUE;
    }

}

-(void)parser:(NSXMLParser *) parser foundCharacters:(NSString *)string
{
    if (elementFoundPortFolio)
    {
        [soapResultsPortFolio appendString: string];
    }      
}

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError
{
    NSLog(@"Parser error %@ ",[parseError description]);
}


//---when the end of element is found---
-(void)parser:(NSXMLParser *)parser 
didEndElement:(NSString *)elementName 
 namespaceURI:(NSString *)namespaceURI 
qualifiedName:(NSString *)qName
{
    if ([elementName isEqualToString:@"GetPortfolioListResult"])
    {          
        NSLog(@"display the soap results%@",soapResultsPortFolio);
    }
    else if([elementName isEqualToString:@"your_tag_name"])
    {          
        //Perform required action
    }
    else if([elementName isEqualToString:@"your_tag_name"])
    {
        //Perform required action
    }
    else if([elementName isEqualToString:@"your_tag_name"])
    {
        //Perform required action
    }

    [soapResultsPortFolio setString:@""];
    elementFoundPortFolio = FALSE;
}

编辑 ：

if ([elementName isEqualToString:@"media:thumbnail"])
{
      //Save your URL in an Array
 }