Having trouble understanding NSXMLParser - iphone

Question

Im having trouble understanding NSXMLParser. I have tried some external XML Parsers but i have had no luck. What i am trying to do is parse the GDATA Youtube API xml which retrieves the xml for videos. This is working fine i have the xml but its difficult reiterating through the elements. I just need an example that can retrieve the elements such as (media:thumbnail url="" )(/media:thumbnail)
How to i get the url value from the element media:thumbnail
The url i am requesting is https://gdata.youtube.com/feeds/api/videos?q=football+-soccer&orderby=published&start-index=11&max-results=10&v=2

Answer 1

This is how you can use NSXMLParser :
In your .h file declare :
NSMutableData *webPortFolio;
NSMutableString *soapResultsPortFolio;
NSURLConnection *conn;
//---xml parsing---
NSXMLParser *xmlParserPortFolio;
BOOL elementFoundPortFolio;
NSMutableURLRequest *req;
NSString *theXMLPortFolio;
NSString *strSoapMsg;
UIAlertView *alertView;
In your .m file use the following code:
-(void)callURL
{
//Your logic to call URL.
conn = [[NSURLConnection alloc] initWithRequest:req delegate:self];
if (conn)
{
webPortFolio = [[NSMutableData data] retain];
}
}
And to handle the response you can use following functions :
-(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;
}
EDIT :
if ([elementName isEqualToString:#"media:thumbnail"])
{
//Save your URL in an Array
}