giving nil while accessing the nsmutable array - iphone

Question

i am parsing a json object and storing the song objects in songs, a nsmutable array.
while am displaying the image of the song i.e. while accessing the object from the array its giving all values nil in that object.
in the following code in setSongsScrollView method, in for loop while accessing the song object from songs array its showing nill in the debugger and crashing with error EXEBadacess.But the count of that array is giving correct.
can any body help me out please
- (void)viewWillAppear:(BOOL)animated{
[super viewDidLoad];
[self parsingTheStation];
[self load_images];
[self setSongsScrollView];
}
/*
// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
}
*/
- (void)parsingTheStation{
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:#"http:...."]];
NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
NSString *jsonString = [[NSString alloc] initWithData:response encoding:NSUTF8StringEncoding];
NSData *jsonData = [jsonString dataUsingEncoding:NSUTF32BigEndianStringEncoding];
NSDictionary *dictionary = [[CJSONDeserializer deserializer] deserializeAsDictionary:jsonData error:nil];
songs =[[NSMutableArray alloc]init];
NSArray *songObjects = [dictionary objectForKey:#"songs"];
for(NSDictionary *s in songObjects){
aSong = [[Song alloc] init];
aSong.artist = [s objectForKey:#"by"];
aSong.genre = [s objectForKey:#"genre"];
aSong.cover = [s objectForKey:#"cover"];
aSong.song_id = [s objectForKey:#"id"];
aSong.rank = [s objectForKey:#"rank"];
aSong.title = [s objectForKey:#"title"];
aSong.link = [s objectForKey:#"link"];
[songs addObject:aSong];
[aSong release];
}
NSLog(#"total number of songs is : %d",[songs count]);
}
-(void)setSongsScrollView {
songsContainer = [[UIScrollView alloc]init];
int songsCount = [self.songs count];
//totla no. of songs we get +4
int tSongs = songsCount+4;
int n = sqrt(tSongs);
int p = n,q = n;
int remSongs = tSongs-(n*n);
if(remSongs >= n){
q = q+(remSongs/n);
if((remSongs%n)>0)
q++;
}else q++;
for(int i=0;q>p;i++){
q--;
p++;
}
NSLog(#"total songs..%d",tSongs);
NSLog(#"total rows..%d",q);
NSLog(#"total columns..%d",p);
songsContainer.contentSize = CGSizeMake(120*q, 120*p);
int x =0, y=240, col=1;
for(int i=0;i<songsCount;i++){
CGRect imgFrame = CGRectMake(x, y, 118, 118);
NSLog(#"songs conunt ...%d",[songs count]);
Song *thesong = [[Song alloc]init];
thesong = [self.songs objectAtIndex:i];
NSString *filename = [NSString stringWithFormat:#"%#/%#", [LazyImageView dataPath], [thesong.cover lastPathComponent]];
UIImageView *tempImg = [[UIImageView alloc] initWithImage:[UIImage imageWithContentsOfFile:filename]];
tempImg.tag = i;
tempImg.frame = imgFrame;
[songsContainer addSubview:tempImg];
[tempImg release];
[thesong release];
y += 120;
if(y>=(120*p)){
NSLog(#"total y..%d",y);
col++;
x += 120;
if(col>=3)
y=0;
else
y=240;
}
}
NSLog(#"total y..%d",y);
NSLog(#"content size..%d,%d",120*q,120*p);
}
-(void)load_images{
for(int i=0;i<[songs count];i++){
Song *rsong = [[Song alloc]init];
rsong = [self.songs objectAtIndex:i];
lazyBigImg = [[LazyImageView alloc] init];
NSURL* url = [NSURL URLWithString:rsong.cover];
[lazyBigImg loadImageFromURL:url];
[lazyBigImg release];
[rsong release];
}
}
/*
// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
*/
- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
- (void)viewDidUnload {
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (void)dealloc {
[songs release];
[lazyBigImg release];
[onAirBtn release];
[chartsBtn release];
[dealsBtn release];
[searchBtn release];
[stNameLbl release];
[aSong release];
[songsContainer release];
[super dealloc];
}
#end

Answer 1

Marcel has basically got the right answer but I think a little more explanation is needed. Look at the following lines from setSongsScrollView:
Song *thesong = [[Song alloc]init];
The above line allocates a new Song that you own and assigns a reference to it to thesong
thesong = [self.songs objectAtIndex:i];
The above line replaces that reference with a new reference to a song from the array that you don't own. Remember that: you do not own the song referenced by thesong now. There are now no more references left to the object you just allocated, but you still own it. The object has therefore leaked.
NSString *filename = [NSString stringWithFormat:#"%#/%#", [LazyImageView dataPath], [thesong.cover lastPathComponent]];
Use stringByAppendingPathComponent: to build file paths, not stringWithFormat:.
UIImageView *tempImg = [[UIImageView alloc] initWithImage:[UIImage imageWithContentsOfFile:filename]];
tempImg.tag = i;
tempImg.frame = imgFrame;
[songsContainer addSubview:tempImg];
[tempImg release];
[thesong release];
The last line in the above sequence releases the object referenced by thesong. As noted above, you do not own that object. You must not release it, but you have anyway. This means that, at some point, may be now, maybe later, the object will be deallocated while something (probably the array) still thinks it has a valid reference. That's what causes the crash.
-(void)load_images{
for(int i=0;i<[songs count];i++){
Song *rsong = [[Song alloc]init];
rsong = [self.songs objectAtIndex:i];
lazyBigImg = [[LazyImageView alloc] init];
NSURL* url = [NSURL URLWithString:rsong.cover];
[lazyBigImg loadImageFromURL:url];
[lazyBigImg release];
[rsong release];
}
}
The above method contains exactly the same error.

Answer 2

You're creating a new Song instance (thesong), then assign this very instance to a song presumably already in the array. That makes no sense at all and is probably responsible for the memory error.
You shouldn't need to be creating new Songs if they are already in the array. Instead:
Song *thesong = [self.songs objectAtIndex:i];
Also look into using the Objective-C 2.0 for-each loop syntax.