Programme crashes when add dictionary to array? - iphone

Question

I have a crash problem when I am trying to add object into array, I think I have problem with the way i create object and release it. But I am not quite sure cause I am still kinda weak with memory management
NSMutableDictionary *schools = [[NSMutableDictionary alloc] init];
[schools setObject:name forKey:kFavoriteSchoolName];
//load data is getting data from NSUserDefault which I save
NSMutableArray *loadedArray = [self loadData];
//if loadedarray has object in there, then continue adding schools to it or make new array
if([loadedArray count] > 0)
{
[loadedArray addObject:schools];
> // it crashes here
[schools release];
return loadedArray;
} else
{
//It will add the school to the array for the first time if there is nothing when it loaded.
NSMutableArray *tempArray = [[[NSMutableArray alloc] init] autorelease];
[tempArray addObject:schools];
[schools release];
return tempArray;
}
This function help add the school into favorite list. I cant add once, but it crashes when I add it again.
This is my code of loadData function
- (NSMutableArray *) loadData
{
   NSUserDefaults *userDefault = [NSUserDefaults standardUserDefaults];
   
   NSMutableArray *list = [userDefault objectForKey:kSchoolList];
   
   return list;
   
}
The log does not say anything but this: Thread 1: Program received signal "SGABRT"
when I first run the programme and add, it is fine, I add school again then only it crashes, crashes at [loadedArray addobject:schools];

Answer 1

Your code looks clear. The only white spot is the way you create array in [self loadData] method.
You mentioned that you restore it from NSUserDefaults. Probably you just return it by [[NSUserDefaults standardUserDefaults] objectForKey:#"schools"].
Since objectForKey: method returns id type object you don't get a warning telling that objectForKey: returns NSArray not NSMutableArray.
Just make something like this:
return [NSMutableArray arrayWithArray:[[NSUserDefaults standardUserDefaults] objectForKey:#"schools"]];
I hope I guessed your code right ;)

Answer 2

It would help if you put up the log, so we'll know what the crash actually is. I assume at some point you are storing values of tempArray into loaded. Try changing your code to this
NSMutableDictionary *schools = [[NSMutableDictionary alloc] init];
[schools setObject:name forKey:kFavoriteSchoolName];
//load data is getting data from NSUserDefault which I save
NSMutableArray *loadedArray = [[self loadData] retain];
//if loadedarray has object in there, then continue adding schools to it or make new array
if([loadedArray count] > 0)
{
if([loadedArray isKindOfClass:[NSMutableArray class]]) {
[loadedArray addObject:schools];
}
else {NSLog(#"Not a mutable array");}
> // it crashes here
[schools release];
return [loadedArray autorelease];
} else
{
[loadedArray release];
//It will add the school to the array for the first time if there is nothing when it loaded.
NSMutableArray *tempArray = [[[NSMutableArray alloc] init] autorelease];
[tempArray addObject:schools];
[schools release];
return tempArray;
}

Answer 3

I found out that you didn't initialize your array loadArray. You
cannot add any value to uninitialized NSMutableArray.
You need to start with initialization.
NSMutableArray *loadArray = [[NSMutableArray alloc]init];
Then populate data to your array
[loadArray addObjectsFromArray:[self loadData]];