Memory Problems with Array Property

[macz]

Hi all,

I've got some problems to keep the values in an array-property:

There is an UITableViewController which has an property books:

@property (nonatomic, retain) NSArray *books;

In it's loadView method the UITableViewController requests some data from a webservice (which is a class by its own, referenced in the ApplicationDelegate). When the webservice has finished his asynchronous request he calls back a method on the UITableViewController, delivering a piece of XML:

- (void)didGetBooksForController:(GDataXMLElement *)returnNode {
	
	NSArray *booksXML = [returnNode elementsForName:@"item"];
	//NSLog(@"%@", returnNode);
	self.books = [NSArray array];
	for (GDataXMLElement *bookXML in booksXML) {
		NSLog(@"%@", bookXML);
		Book *aBook = [[Book alloc] initWithXML:bookXML];
		self.books = [self.books arrayByAddingObject:aBook];
		[aBook release];
	}
	[self.tableView reloadData];
}

All works fine - the returnNode XML holds the data I was looking for, the array holds the number of objects I expected.
The last line in the previous method initiates the UITableView to ask his delegate (my UITableViewController) to provide him with data for the cells:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    
    static NSString *CellIdentifier = @"Cell";
    
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
    }
    
	NSUInteger row = [indexPath row];
	NSUInteger section = [indexPath section];
	
	if (books != nil) {
		
		switch (section) {
			case 0: {
				Book *aBook = [self.books objectAtIndex:row] ;	
				cell.textLabel.text = aBook.mediatitle;
                                [aBook release];
				break;
			}
			case 1:
				cell.textLabel.text = @"Scenario";
				break;
			default:
				break;
		}
	}
    return cell;
}

but unfortunatly the property self.books seems to be gone!

I'am sure I've got some issues with my retainCount, but I can't figure out which variable to retain without leaving memory unreleased.

[wuf810]

Not sure but shouldn't books be a mutable array?

[macz]

Originally Posted by wuf810

Not sure but shouldn't books be a mutable array?

I had the same idea, but the result was disappoiting ...

Meanwhile I've got it working:

I retain the mediatitle property in the initWithXML: method after extracting its value from the XML.

I am not sure in doing this, cause allthough the XML is an autoreleased object, which doesn't survive the eventcycle, assigning it to the property mediatitle should retain it for the livetime of the book object.

[wuf810]

Originally Posted by macz

I had the same idea, but the result was disappoiting ...

Meanwhile I've got it working:

I retain the mediatitle property in the initWithXML: method after extracting its value from the XML.

I am not sure in doing this, cause allthough the XML is an autoreleased object, which doesn't survive the eventcycle, assigning it to the property mediatitle should retain it for the livetime of the book object.

Yes that makes sense. Better still would be to create a class called books and create an instance of books (during the init assign the attributes you retrieved to instance variable) and then add the book object to your array.

M.

[macz]

Originally Posted by wuf810

Yes that makes sense. Better still would be to create a class called books and create an instance of books (during the init assign the attributes you retrieved to instance variable) and then add the book object to your array.
M.

ehm - isn't that exactly what I am doing? I've got a class Book - in initWithXML I am assigning the xml-attributes to instance variables - finally I add the aBook-instance to my Array books.

[macz]

Retaining the properties in the Book-class does the job only on first sight:

When I scroll a table-cell out of sight and back again (which invokes ..cellForRowAtIndexPath... again) my app crashes: no more books in the array!

[wuf810]

Originally Posted by macz

ehm - isn't that exactly what I am doing? I've got a class Book - in initWithXML I am assigning the xml-attributes to instance variables - finally I add the aBook-instance to my Array books.

oops sorry yes, I wasn't concentrating.

[wuf810]

Originally Posted by macz

Retaining the properties in the Book-class does the job only on first sight:

When I scroll a table-cell out of sight and back again (which invokes ..cellForRowAtIndexPath... again) my app crashes: no more books in the array!

I've lost track of the changes you've made...do you want to re post the latest code.

[macz]

Originally Posted by wuf810

I've lost track of the changes you've made...do you want to re post the latest code.

thank you for your engagement - but finally I diceded to rethink my design.
All in all it boils to down to one question.

This is the initializer of my Book class:

- (id)initWithXML:(GDataXMLElement *)theXML {
	
    self = [super init];
    if (self) {
		NSArray *mediatitles = [theXML elementsForName:@"mediatitle"];
		if (mediatitles.count > 0) {
			GDataXMLElement *anTitle = (GDataXMLElement *) [mediatitles objectAtIndex:0];
			self.mediatitle  = anTitle.stringValue;
			[self.mediatitle retain];
		}
    }

	
    return self;
}

Why do I have to retain mediatitle?
I thought invoking the synthesized setter would do this for me (and btw force me to release all my properties in the dealloc method)

[wuf810]

Originally Posted by macz

thank you for your engagement - but finally I diceded to rethink my design.
All in all it boils to down to one question.

This is the initializer of my Book class:

- (id)initWithXML:(GDataXMLElement *)theXML {
	
    self = [super init];
    if (self) {
		NSArray *mediatitles = [theXML elementsForName:@"mediatitle"];
		if (mediatitles.count > 0) {
			GDataXMLElement *anTitle = (GDataXMLElement *) [mediatitles objectAtIndex:0];
			self.mediatitle  = anTitle.stringValue;
			[self.mediatitle retain];
		}
    }

	
    return self;
}

Why do I have to retain mediatitle?
I thought invoking the synthesized setter would do this for me (and btw force me to release all my properties in the dealloc method)

You are correct, you shouldn't need to. Sorry, I know that isn't much help…

[macz]

Originally Posted by wuf810

You are correct, you shouldn't need to. Sorry, I know that isn't much help…

thanks mate - you made my day!