Objective-C 'RootViewController' may not respond to '-parseXMLFileAtURL:' error in xCode - objective-c

Question

I have this error when building and running my project in xCode:
RootViewController may not respond to -parseXMLFileAtURL:
I'm attempting to develop the basic Apple RSS Reader from the tutorial at:
http://gigaom.com/apple/tutorial-build-a-simple-rss-reader-for-iphone/
my section of code that this error is occurring in looks like this:
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
if ([stories count] == 0)
{
NSString * path = #"http://feeds.feedburner.com/TheAppleBlog";
[self parseXMLFileAtURL:path];
}
cellSize = CGSizeMake([newsTable bounds].size.width, 60);
}
can anybody explain why this parseXMLFileAtURL command gives so much heartache?
Thanks
UPDATED***
I also define parseXMLFileAtURL in the same file; however, I placed that section of the code after the viewDidAppear method (my bad). So when I change the order of the methods that error goes away. But when I do that, I get another error, maybe you guys can help with that error too! here it is:
Class RootViewController does not implement the NSXMLParserDelegate protocol
within this section of code:
- (void)parseXMLFileAtURL:(NSString *)URL
{
stories = [[NSMutableArray alloc] init];
NSURL *xmlURL = [NSURL URLWithString:URL];
rssParser = [[NSXMLParser alloc] initWithContentsOfURL:xmlURL];
[rssParser setDelegate:self];
[rssParser setShouldProcessNamespaces:NO];
[rssParser setShouldReportNamespacePrefixes:NO];
[rssParser setShouldResolveExternalEntities:NO];
[rssParser parse];
}
The error occurs after the line: [rssParser setDelegate:self]; - what might be wrong with that?

Answer 1

In regards to your second question that RootViewController does not conform to the NSXMLParserDelegate protocol. Just add it like this in your RootViewController.h file:
#interface RootViewController : UIViewController <NSXMLParserDelegate> { .....

Answer 2

Silly question: Does your RootViewcontroller class have a method named -parseXMLFileAtURL: defined? If -parseXMLFileAtURL: comes after the method that calls it, you'll also need to declare it in your header.

Answer 3

Make sure you have parseXMLFileAtURL defined in your RootViewController.m
-(void)parseXMLFileAtURL:(NSString *)url
{
...
}
And make sure you have it defined in your header as:
-(void)parseXMLFileAtURL:(NSString *)url;
Also, make sure that when you try to get the contents from the web, you're using an NSURL, not an NSString. You can instantiate a NSURL with a string by:
NSURL *urlFromString = [[NSURL alloc] initWithString:#"http://..."];