Question

Ok, I spent the last 8 hours fighting with it – it just seems beyond me. Here’s my complete (relevant) code:

- (void)updateUserDefaults
{
    NSMutableDictionary *viewControllerDetails = [[NSMutableDictionary alloc] initWithCapacity:4];

    [viewControllerDetails setObject:[NSNumber numberWithInt:OOVenueClassControllerType] forKey:@"classType"];
    [viewControllerDetails setObject:self.searchTerm forKey:@"searchTerm"];
    [viewControllerDetails setObject:self.searchLocation forKey:@"searchLocation"];

    //----- the next two lines cause the problem
    NSString *res = [[NSString stringWithFormat:@"%@",[searchResults xmlString]] retain];
    [viewControllerDetails setObject:res forKey:@"searchresults"];
    //-----

    NSMutableArray *viewControllersList = [NSMutableArray array] ;
    [viewControllersList addObject:viewControllerDetails];

    NSUserDefaults *defs = [NSUserDefaults standardUserDefaults];
    //the following line causes the error
    [defs setObject:viewControllersList forKey:kViewControllersKey];
    [defs synchronize];

    [res release];
}

Note the block with the next two lines cause the problem. At first I didn’t create another string, but added it later while trying to solve the problem.

If I comment out those two lines, everything works fine. If I put them back in, I get

- [CFString class]: message sent to deallocated instance 0xa1a9000

Is something is wrong with the string that I’m trying to put into the userdefaults? That string is rather large (about 200,000 characters), but I had stored even longer strings in user defaults in the past.

It’s also worth noting that if I uninstall the app, then everything works fine. But on subsequent runs the problem exhibits itself.

So, how and why and where is the string getting deallocated? I have explicitly added retain – but that still doesn’t help. What am I missing?

Edit: just realised I forgot to say that the error is thrown on line

[defs setObject:viewControllersList forKey:kViewControllersKey];

Also, for general information, method - (NSString *)xmlString on searchResults does exactly what the name means: creates an XML string with the information from that object.

Edit 2: I tried doing something else with that string – convert it to NSData, compress using zlib – but regardless of data type, that particular object gets deallocated. Does it have to do something with the size of the string?

Answer 1

Ok, not sure what exactly the problem was, but it was somewhere in the searchResults and/or xmlString method. searchResults object is originally created from XML received from the server (XML is parsed into the object structure). When xmlString was called, for some reason the string I was getting back was different from the original XML (I’m not talking about formatting, of course) – of 200,000 char-long string, within the first 500 chars or so there were some differences. I haven’t been able to figure out why. So, instead of recreating the xml from object structure, I instead stored the original XML in a field in that object and, when xmlString was called, simply returned the original string. Now everything worked fine.

Thank you all for your support through this painful process.