scrolling tableview causes crash

Question

I am facing a simple yet annoying problem of memory deallocation and message sending to a freed object.

I am trying to get Rss feed from a web page. I developed the applet in 2 stages, in stage one , as i am yet new to iphone development i tried getting the text part of an Rss feed from a webpage with success and no problems. In stage 2 i tried getting the links to images and presenting them both on each UITableViewCell and the detailed view afterwards.

i have a class that loads the rss and is responsible for the parsing and the returning of the mutable array which i return through [array copy]. everything works well, even though it takes some time to load. When i Run the app and try to scroll the table view i get a crash and an NSZombie message :

objc[37372]: FREED(id): message retain sent to freed object=0x3930cd0

and this happens also when i try to load the detailViewController without scrolling i post some of the tableViewController to see what is wrong.

- (void)viewDidLoad {
    [super viewDidLoad];
    post = [[Posts alloc]init];
    //self.tableView.rowHeight = 160.0;
    self.navigationController.navigationBar.barStyle = UIBarStyleBlack;
    self.navigationController.navigationBar.tintColor = [UIColor purpleColor];
    NSLog(@"parser is about to init");
    parser = [[XmlParser alloc] init];
    array = [parser initWithURL:@"http://backend.deviantart.com/rss.xml?q=boost%3Apopular+meta%3Aall+max_age%3A8h&type=deviation&offset=0"];
    //array = [parser initWithURL:@"http://www.enet.gr/rss?i=news.el.categories&c=politikh"];
    NSLog(@"posts has %d items",[array count]);
    [parser release];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView  dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
        post = [array objectAtIndex:indexPath.row];
        // Set up the cell...
        [cell.textLabel text:[post itemTitle]];
        [cell.detailTextLabel setText:[post itemBody]];
        [cell.imageView setImage:[self.post itemthumbnail]];

    }
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    // Navigation logic may go here. Create and push another view controller.
     FirstDetailedViewController *anotherViewController = [[[FirstDetailedViewController alloc] initWithNibName:@"FirstDetailedViewController" bundle:nil]autorelease];
    NSLog(@"posts count : %d", [array count]);
    post = [array objectAtIndex:indexPath.row];
    anotherViewController.currpost = [post retain];
    [self.navigationController pushViewController:anotherViewController animated:YES];
}

The post clash is some NSMutableStrings and UIImages, all of them are allocated and initialized in their own init and dealloced in their own dealloc method. I am also having problem when i try to tap on a cell without scrolling but that's tommorows problem.

Answer 1

Solved it! simple init problem

Previous :

    -(id)init
{   
    [super init];
    channelTitle = [[NSMutableString alloc]init];
    channelLink = [[NSMutableString alloc]init];
    channelDescription = [[NSMutableString alloc]init];
    channelPubDate = [[NSMutableString alloc]init];
    itemTitle = [[NSMutableString alloc]init];
    itemBody =  [[NSMutableString alloc]init];
    itemPubDate = [[NSMutableString alloc]init];
    itemLink = [[NSMutableString alloc]init];
    itemthumbnail = [[UIImage alloc]init];
    itemthumbnailLink = [[NSString alloc]init];
    itemImage = [[UIImage alloc]init];
    itemImageLink = [[NSString alloc]init];
    return self;
}

Now :

-(id)init
{   
    if (self==[super init]){
    channelTitle = [[NSMutableString alloc]init];
    channelLink = [[NSMutableString alloc]init];
    channelDescription = [[NSMutableString alloc]init];
    channelPubDate = [[NSMutableString alloc]init];
    itemTitle = [[NSMutableString alloc]init];
    itemBody =  [[NSMutableString alloc]init];
    itemPubDate = [[NSMutableString alloc]init];
    itemLink = [[NSMutableString alloc]init];
    itemthumbnail = [[UIImage alloc]init];
    itemthumbnailLink = [[NSString alloc]init];
    itemImage = [[UIImage alloc]init];
    itemImageLink = [[NSString alloc]init];
    }
    return self;
}

the actual image was never allocated! now it is! :D

Answer 2

if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    post = [array objectAtIndex:indexPath.row];
    // Set up the cell...
    [cell.textLabel text:[post itemTitle]];
    [cell.detailTextLabel setText:[post itemBody]];
    [cell.imageView setImage:[self.post itemthumbnail]];

}
return cell;}

You don't wan't to configure each cell for display at this place in the code. Your code should look something like this:

    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    }
    post = [array objectAtIndex:indexPath.row];
    // Set up the cell...
    [cell.textLabel text:[post itemTitle]];
    [cell.detailTextLabel setText:[post itemBody]];
    [cell.imageView setImage:[self.post itemthumbnail]];

   return cell;
}

Answer 3

Most likely a problem with your data source being auto-released prematurely. Try and retain the array object or declare a (retain) property for it and in your viewDidLoad method:

NSArray *tmpArray = [parser initWithURL:@"http://backend.deviantart.com/rss.xml?q=boost%3Apopular+meta%3Aall+max_age%3A8h&type=deviation&offset=0"];
self.array = tmpArray;

Hope if helps. Rog