//
//  RssParser.h
//  RSS
//
//  Copyright 2008 WillowTree Consulting Group, Inc. All rights reserved.
//

#import <Foundation/Foundation.h>


@interface RssParser : NSObject {
@private
        NSMutableDictionary *root;
        NSMutableDictionary *itemsDictionary;
        NSMutableArray *items;
        NSMutableData *webData;
       
        NSString *requestUrl;
        NSString *currentElement;
        BOOL success;
        BOOL loading;
        BOOL parsed;
       
        BOOL inItem;
       
        NSInteger callId;
        id parentDelegate;
        SEL onCompleteCallback;
}

- (id)init:(NSInteger)identifier;
- (void)parse:(NSString *)url withDelegate:(id)sender onComplete:(SEL)callback;
- (void)parseResponse;

- (NSDictionary *)getRoot;
- (NSArray *)getItems;
- (NSInteger)getId;

- (BOOL)isSuccessful;
- (BOOL)isLoading;
- (BOOL)isParsed;

@end



//
//  RssParser.m
//  RSS
//
//  Copyright 2008 WillowTree Consulting Group, Inc. All rights reserved.
//

#import "RssParser.h"


@implementation RssParser

- (id) init:(NSInteger)identifier {
        self = [super init];
       
        if (self) {
                callId = identifier;
                root = [[NSMutableDictionary alloc] init];
                items = [[NSMutableArray alloc] init];
                success = NO;
                loading = NO;
                parsed = NO;
                currentElement = nil;
        }
       
        return self;
}

- (void)parse:(NSString *)url withDelegate:(id)sender onComplete:(SEL)callback {
        parentDelegate = sender;
        onCompleteCallback = callback;
        requestUrl = [url retain];
        loading = YES;
       
        NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
       
        [request setURL:[[NSURL alloc] initWithString:requestUrl]];
        [request setHTTPMethod:@"GET"];
        [request setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];
       
        [[NSURLConnection alloc] initWithRequest:request delegate:self];
        [request release];
       
        webData = [[NSMutableData data] retain];
}

- (BOOL)isSuccessful {
        return success;
}

- (BOOL)isLoading {
        return loading;
}

- (BOOL)isParsed {
        return parsed;
}

- (NSInteger)getId {
        return callId;
}

- (NSArray *)getItems {
        return items;
}

- (NSDictionary *)getRoot {
        return root;
}

// HTTP Request Handling functionality
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
        success = NO;
        loading = NO;
       
        if ([parentDelegate respondsToSelector:onCompleteCallback]) {
                [parentDelegate performSelector:onCompleteCallback withObject:self];
        }
}

- (void)connection:(NSURLConnection *)connection didReceivedAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge {
        success = NO;
}

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

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
        if ([response isKindOfClass:[NSHTTPURLResponse class]]) {
                NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *) response;
               
                NSLog(@"RssParser: Response is an NSHTTPURLResponse: Response=%d", [httpResponse statusCode]);
               
                // Does not handle authentication quite yet.
                if ([httpResponse statusCode] >= 400 && [httpResponse statusCode] <= 599) {
                        success = NO;
                } else if ([httpResponse statusCode] >= 100 && [httpResponse statusCode] <= 299) {
                        success = YES;
                } else {
                        NSLog(@"RssParser: Status code is unknown.");
                }
        }
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
        NSString *dataString = [[[NSString alloc] initWithData:webData encoding:NSASCIIStringEncoding] autorelease];
       
        if ([dataString length] > 0) {
                [self parseResponse];
        }
       
        loading = NO;
}

- (void)parseResponse {
        NSXMLParser *parser = [[NSXMLParser alloc] initWithData:webData];
       
        [parser setDelegate:self];
        [parser setShouldProcessNamespaces:NO];
        [parser setShouldReportNamespacePrefixes:NO];
        [parser setShouldResolveExternalEntities:NO];
       
        [parser parse];
}

// XML Parser functionality

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError {
        NSLog(@"RestResponse: Parsing error occurred.");
        parsed = NO;
        loading = NO;
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI
 qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict {
        NSString *element = [elementName stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
       
        currentElement = element;
       
        if ([[currentElement lowercaseString] isEqual:@"item"]) {
                inItem = YES;
                itemsDictionary = [[NSMutableDictionary alloc] init];
        }
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI
 qualifiedName:(NSString *)qName {
        NSString *element = [elementName stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
       
        if ([[element lowercaseString] isEqual:@"item"]) {
                inItem = NO;
                [items addObject:itemsDictionary];
        }
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {
        NSString *stringValue = [string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
        NSString *element = [currentElement stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
       
        // Skip over blank elements.
        if (stringValue == nil || [stringValue isEqual:@""]) {
                return;
        }
       
        if (element != nil && [element length] > 0) {
                if (inItem) {
                        if ([itemsDictionary objectForKey:element] != nil) {
                                // If we're adding categories, we can safely add a comma.  Otherwise, we don't, and append the string data.
                                if ([element isEqual:@"category"]) {
                                        [itemsDictionary setObject:[NSString stringWithFormat:@"%@, %@", [itemsDictionary objectForKey:element], stringValue]
                                                                forKey:element];
                                } else {
                                        [itemsDictionary setObject:[NSString stringWithFormat:@"%@%@", [itemsDictionary objectForKey:element], stringValue]
                                                                                forKey:element];
                                }
                        } else {
                                [itemsDictionary setObject:stringValue forKey:element];
                        }
                } else {
                        if ([root objectForKey:element] != nil) {
                                if ([element isEqual:@"category"]) {
                                        [root setObject:[NSString stringWithFormat:@"%@, %@", [root objectForKey:element], stringValue] forKey:element];
                                } else {
                                        [root setObject:[NSString stringWithFormat:@"%@%@", [root objectForKey:element], stringValue] forKey:element];
                                }
                        } else {
                                [root setObject:stringValue forKey:element];
                        }
                }
        }
}

- (void)parserDidStartDocument:(NSXMLParser *)parser {
        NSLog(@"RssParser: Started document.");
}

- (void)parserDidEndDocument:(NSXMLParser *)parser {
        parsed = YES;
        loading = NO;


        if ([parentDelegate respondsToSelector:onCompleteCallback]) {
                [parentDelegate performSelector:onCompleteCallback withObject:self];
        }
}


- (void)dealloc {
        [super dealloc];
       
        [requestUrl release];
        requestUrl = nil;
       
        [webData release];
        webData = nil;
}

@end

http://code.google.com/p/iphone-simple-rss-aggregator/source/browse/trunk/Simple+RSS/Classes/RssParser.m

I'm using this Rss Parser for clubplanet app, it works really fast and easy to implement

RssParser that works

xml

Objective C