How to parse data from a website using NSXMLParser - ios

Question

I want to get the updates from a website based on the titles and links which is in xml format.
I have tried with the code below but it's not working. In console it is showing the message:
2011-11-03 14:45:05.987 tabbar[673:e903] * Terminating app due to
uncaught exception 'NSInvalidArgumentException', reason: '-[NSCFString
isEqualtostring:]: unrecognized selector sent to instance 0x5746830'
If I run again, the table view is loading but there is no data in the table cells.
It is showing this message at the line if ([elementName isEqualtostring:#"item"]):
program received signal SIGABRT
-(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
classelement = elementName;
if ([elementName isEqualtostring:#"item"])
{
itemselected = YES;
multitle = [[NSMutableString alloc]init];
mullink = [[NSMutableString alloc]init];
}
}
-(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedname:(NSString *)qName
{
if ([elementName isEqualToString:#"item"])
{
itemselected = NO;
[titlearray addObject:multitle];
[linkarray addObject:mullink];
[multitle release];
[mullink release];
[self.tbl reloadData];
}
}
-(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
if (itemselected)
{
if ([classelement isEqualToString:#"title"])
{
NSLog(#"%#",string);
[multitle appendString:multitle];
}
else if([classelement isEqualToString:#"link"])
{
[multitle appendString:string];
}
}
}

Answer 1

If you are reading directly from a website more than likely you are getting "invalid" characters. As soon as the parser see's these invalid characters it will crash. I would suggest looking at using "HPPLE Parser". It works much better and wont crash if invalid characters come in.
Hpple information here: http://blog.objectgraph.com/index.php/2010/02/24/parsing-html-iphone-development/

Answer 2

Finally I got it. What I did is I have taken two NSMutableArrays and two NSMutableStrings and I appended the items to the strings, and later those strings I appended to the two arrays.
(void)viewDidLoad
{
titlearray = [[NSMutableArray alloc]init];
linkarray = [[NSMutableArray alloc]init];
NSString *rssaddress =#"http://www.greenday.com/rss";
NSURL *url = [NSURL URLWithString:rssaddress];
xmlparser = [[NSXMLParser alloc]initWithContentsOfURL:url];
[xmlparser setDelegate:self];
[xmlparser parse];
[super viewDidLoad];
}
(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
classelement = elementName;
if([elementName isEqualToString:#"item" ])
{
itemselected = YES;
titlestrng = [[NSMutableString alloc]init];
linkstrng = [[NSMutableString alloc]init];
}
}
(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
if([elementName isEqualToString:#"item" ])
{
itemselected = NO;
[titlearray addObject:titlestrng];
[linkarray addObject:linkstrng];
[titlestrng release];
[linkstrng release];
[self.tb reloadData];
}
}
(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
if(itemselected)
{
if([classelement isEqualToString:#"title"])
{
[titlestrng appendString: string];
NSLog(#"%#",titlestrng);
}
else if ([classelement isEqualToString:#"link"])
{
[linkstrng appendString:string];
NSLog(#"%#",linkstrng);
}
}
}