Iphone NSXMLParser NSCFString memory leak - iphone

Question

I am building an app that parses an rss feed. In the app there are two different types of feeds with different names for the elements in the feed, so I have created an NSXMLParser NSObject that takes the name of the elements of each feed before parsing. Here is my code:
NewsFeedParser.h
#import
#interface NewsFeedParser : NSObject {
NSInteger NewsSelectedCategory;
NSXMLParser *NSXMLNewsParser;
NSMutableArray *newsCategories;
NSMutableDictionary *NewsItem;
NSMutableString *NewsCurrentElement, *NewsCurrentElement1, *NewsCurrentElement2, *NewsCurrentElement3;
NSString *NewsItemType, *NewsElement1, *NewsElement2, *NewsElement3;
NSInteger NewsNumElements;
}
- (void) parseXMLFileAtURL:(NSString *)URL;
#property(nonatomic, retain) NSString *NewsItemType;
#property(nonatomic, retain) NSString *NewsElement1;
#property(nonatomic, retain) NSString *NewsElement2;
#property(nonatomic, retain) NSString *NewsElement3;
#property(nonatomic, retain) NSMutableArray *newsCategories;
#property(assign, nonatomic) NSInteger NewsNumElements;
#end
NewsFeedParser.m
#import "NewsFeedParser.h"
#implementation NewsFeedParser
#synthesize NewsItemType;
#synthesize NewsElement1;
#synthesize NewsElement2;
#synthesize NewsElement3;
#synthesize newsCategories;
#synthesize NewsNumElements;
- (void)parserDidStartDocument:(NSXMLParser *)parser{
}
- (void)parseXMLFileAtURL:(NSString *)URL
{
newsCategories = [[NSMutableArray alloc] init];
URL = [URL stringByReplacingOccurrencesOfString:#" " withString:#""];
URL = [URL stringByReplacingOccurrencesOfString:#"\n" withString:#""];
URL = [URL stringByReplacingOccurrencesOfString:#" " withString:#""];
//you must then convert the path to a proper NSURL or it won't work
NSURL *xmlURL = [NSURL URLWithString:URL];
// here, for some reason you have to use NSClassFromString when trying to alloc NSXMLParser, otherwise you will get an object not found error
// this may be necessary only for the toolchain
[[NSURLCache sharedURLCache] setMemoryCapacity:0];
[[NSURLCache sharedURLCache] setDiskCapacity:0];
NSXMLNewsParser = [[NSXMLParser alloc] initWithContentsOfURL:xmlURL];
// Set self as the delegate of the parser so that it will receive the parser delegate methods callbacks.
[NSXMLNewsParser setDelegate:self];
// Depending on the XML document you're parsing, you may want to enable these features of NSXMLParser.
[NSXMLNewsParser setShouldProcessNamespaces:NO];
[NSXMLNewsParser setShouldReportNamespacePrefixes:NO];
[NSXMLNewsParser setShouldResolveExternalEntities:NO];
[NSXMLNewsParser parse];
[NSXMLNewsParser release];
}
- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError {
NSString * errorString = [NSString stringWithFormat:#"Unable to download story feed from web site (Error code %i )", [parseError code]];
NSLog(#"error parsing XML: %#", errorString);
UIAlertView * errorAlert = [[UIAlertView alloc] initWithTitle:#"Error loading content" message:errorString delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil];
[errorAlert show];
[errorAlert release];
[errorString release];
}
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict{
NewsCurrentElement = [elementName copy];
if ([elementName isEqualToString:NewsItemType])
{
// clear out our story item caches...
NewsItem = [[NSMutableDictionary alloc] init];
NewsCurrentElement1 = [[NSMutableString alloc] init];
NewsCurrentElement2 = [[NSMutableString alloc] init];
if(NewsNumElements == 3)
{
NewsCurrentElement3 = [[NSMutableString alloc] init];
}
}
}
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{
if ([elementName isEqualToString:NewsItemType])
{
// save values to an item, then store that item into the array...
[NewsItem setObject:NewsCurrentElement1 forKey:NewsElement1];
[NewsItem setObject:NewsCurrentElement2 forKey:NewsElement2];
if(NewsNumElements == 3)
{
[NewsItem setObject:NewsCurrentElement3 forKey:NewsElement3];
}
[newsCategories addObject:[[NewsItem copy] autorelease]];
[NewsCurrentElement release];
[NewsCurrentElement1 release];
[NewsCurrentElement2 release];
if(NewsNumElements == 3)
{
[NewsCurrentElement3 release];
}
[NewsItem release];
}
}
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
//NSLog(#"found characters: %#", string);
// save the characters for the current item...
if ([NewsCurrentElement isEqualToString:NewsElement1]) {
[NewsCurrentElement1 appendString:string];
} else if ([NewsCurrentElement isEqualToString:NewsElement2]) {
[NewsCurrentElement2 appendString:string];
} else if (NewsNumElements == 3 && [NewsCurrentElement isEqualToString:NewsElement3])
{
[NewsCurrentElement3 appendString:string];
}
}
- (void)dealloc {
[super dealloc];
[newsCategories release];
[NewsItemType release];
[NewsElement1 release];
[NewsElement2 release];
[NewsElement3 release];
}
When I create an instance of the class I do like so:
NewsFeedParser *categoriesParser = [[NewsFeedParser alloc] init];
if(newsCat == 0)
{
categoriesParser.NewsItemType = #"article";
categoriesParser.NewsElement1 = #"category";
categoriesParser.NewsElement2 = #"catid";
}
else
{
categoriesParser.NewsItemType = #"article";
categoriesParser.NewsElement1 = #"category";
categoriesParser.NewsElement2 = #"feedUrl";
}
[categoriesParser parseXMLFileAtURL:feedUrl];
newsCategories = [[NSMutableArray alloc] initWithArray:categoriesParser.newsCategories copyItems:YES];
[self.tableView reloadData];
[categoriesParser release];
If I run the app with the leaks instrument, the leaks point to the [NSXMLNewsParser parse] call in the NewsFeedParser.m.
Here is a screen shot of the Leaks instrument with the NSCFStrings leaking:
http://img139.imageshack.us/img139/3997/leaks.png
For the life of me I can't figure out where these leaks are coming from. Any help would be greatly appreciated.

Answer 1

The leak occurred in the didStartElement method. I was copying elementName without releasing it.
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict{
NewsCurrentElement = [[elementName copy] autorelease];
if ([elementName isEqualToString:NewsItemType])
{
// clear out our story item caches...
NewsItem = [[NSMutableDictionary alloc] init];
NewsCurrentElement1 = [[NSMutableString alloc] init];
NewsCurrentElement2 = [[NSMutableString alloc] init];
if(NewsNumElements == 3)
{
NewsCurrentElement3 = [[NSMutableString alloc] init];
}
}
}

Answer 2

You might also want to release (if necessary) the allocated NSMutableString properties before allocating another NSMutableString into the property like so:
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict {
if (NewsCurrentElement) {
[NewsCurrentElement release], NewsCurrentElement = nil;
}
NewsCurrentElement = [[elementName copy] autorelease];
if ([elementName isEqualToString:NewsItemType]) {
// clear out our story item caches...
if (NewsItem) {
[NewsItem release], NewsItem = nil;
}
NewsItem = [[NSMutableDictionary alloc] init];
if (NewsCurrentElement1) {
[NewsCurrentElement1 release], NewsCurrentElement1 = nil;
}
NewsCurrentElement1 = [[NSMutableString alloc] init];
if (NewsCurrentElement2) {
[NewsCurrentElement2 release], NewsCurrentElement2 = nil;
}
NewsCurrentElement2 = [[NSMutableString alloc] init];
if(NewsNumElements == 3) {
if (NewsCurrentElement3) {
[NewsCurrentElement3 release], NewsCurrentElement3 = nil;
}
NewsCurrentElement3 = [[NSMutableString alloc] init];
}
}
}