Classes/CocoaXMLParser.m

/*
     File: CocoaXMLParser.m
 Abstract: Subclass of iTunesRSSParser that uses the Foundation framework's NSXMLParser for parsing the XML data.
  Version: 1.4
 
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*/
 
#import "CocoaXMLParser.h"
#import "Song.h"
 
@implementation CocoaXMLParser
 
+ (NSString *)parserName {
    return @"NSXMLParser";
}
 
+ (XMLParserType)parserType {
    return XMLParserTypeNSXMLParser;
}
 
@synthesize currentString, currentSong, parseFormatter, xmlData, rssConnection;
 
- (void)downloadAndParse:(NSURL *)url {
 
    done = NO;
    self.parseFormatter = [[NSDateFormatter alloc] init];
    [parseFormatter setDateStyle:NSDateFormatterLongStyle];
    [parseFormatter setTimeStyle:NSDateFormatterNoStyle];
    // necessary because iTunes RSS feed is not localized, so if the device region has been set to other than US
    // the date formatter must be set to US locale in order to parse the dates
    [parseFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"US"]];
    self.xmlData = [NSMutableData data];
    [[NSURLCache sharedURLCache] removeAllCachedResponses];
    NSURLRequest *theRequest = [NSURLRequest requestWithURL:url];
    // create the connection with the request and start loading the data
    rssConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
    [self performSelectorOnMainThread:@selector(downloadStarted)
                           withObject:nil
                        waitUntilDone:NO];
    if (rssConnection != nil) {
        do {
            [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
        } while (!done);
    }
    self.rssConnection = nil;
    self.parseFormatter = nil;
    self.currentSong = nil;
}
 
 
#pragma mark NSURLConnection Delegate methods
 
/*
 Disable caching so that each time we run this app we are starting with a clean slate.
 You may not want to do this in your application.
 */
- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse {
    return nil;
}
 
// Forward errors to the delegate.
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    
    done = YES;
    [self performSelectorOnMainThread:@selector(parseError:)
                           withObject:error
                        waitUntilDone:NO];
}
 
// Called when a chunk of data has been downloaded.
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    
    // Append the downloaded chunk of data.
    [xmlData appendData:data];
}
 
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    
    [self performSelectorOnMainThread:@selector(downloadEnded)
                           withObject:nil
                        waitUntilDone:NO];
    NSXMLParser *parser = [[NSXMLParser alloc] initWithData:xmlData];
    parser.delegate = self;
    self.currentString = [NSMutableString string];
    NSTimeInterval start = [NSDate timeIntervalSinceReferenceDate];
    [parser parse];
    NSTimeInterval duration = [NSDate timeIntervalSinceReferenceDate] - start;
    [self performSelectorOnMainThread:@selector(addToParseDuration:)
                           withObject:[NSNumber numberWithDouble:duration]
                        waitUntilDone:NO];
    [self performSelectorOnMainThread:@selector(parseEnded)
                           withObject:nil
                        waitUntilDone:NO];
    self.currentString = nil;
    self.xmlData = nil;
    // Set the condition which ends the run loop.
    done = YES; 
}
 
 
#pragma mark Parsing support methods
 
static const NSUInteger kAutoreleasePoolPurgeFrequency = 20;
 
- (void)finishedCurrentSong {
    
    // performSelectorOnMainThread: will retain the object until the selector has been performed
    // setting the local reference to nil ensures that the local reference will be released
    //
    [self performSelectorOnMainThread:@selector(parsedSong:)
                           withObject:currentSong
                        waitUntilDone:NO];
    
    self.currentSong = nil;
}
 
 
#pragma mark NSXMLParser Parsing Callbacks
 
// Constants for the XML element names that will be considered during the parse. 
// Declaring these as static constants reduces the number of objects created during the run
// and is less prone to programmer error.
//
static NSString *kName_Item = @"item";
static NSString *kName_Title = @"title";
static NSString *kName_Category = @"category";
static NSString *kName_Artist = @"itms:artist";
static NSString *kName_Album = @"itms:album";
static NSString *kName_ReleaseDate = @"itms:releasedate";
 
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *) qualifiedName attributes:(NSDictionary *)attributeDict {
    
    if ([elementName isEqualToString:kName_Item]) {
        self.currentSong = [[Song alloc] init];
    } else if ([elementName isEqualToString:kName_Title] || [elementName isEqualToString:kName_Category] || [elementName isEqualToString:kName_Artist] || [elementName isEqualToString:kName_Album] || [elementName isEqualToString:kName_ReleaseDate]) {
        [currentString setString:@""];
        storingCharacters = YES;
    }
}
 
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {
 
    if ([elementName isEqualToString:kName_Item]) {
        [self finishedCurrentSong];
    } else if ([elementName isEqualToString:kName_Title]) {
        currentSong.title = currentString;
    } else if ([elementName isEqualToString:kName_Category]) {
        currentSong.category = currentString;
    } else if ([elementName isEqualToString:kName_Artist]) {
        currentSong.artist = currentString;
    } else if ([elementName isEqualToString:kName_Album]) {
        currentSong.album = currentString;
    } else if ([elementName isEqualToString:kName_ReleaseDate]) {
        currentSong.releaseDate = [parseFormatter dateFromString:currentString];
    }
    storingCharacters = NO;
}
 
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {
    if (storingCharacters) [currentString appendString:string];
}
 
/*
 A production application should include robust error handling as part of its parsing implementation.
 The specifics of how errors are handled depends on the application.
 */
- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError {
    // Handle errors as appropriate for your application.
}
 
@end