accessing class file crashes when scrolling starts (UIScrollview) - iphone

Question

hopefully someone will be able to help me. I have a UIScrollView on my page. The .h file has set the UIscrollviewdelegate.
I have a class file called "Picture.h / Picture.m".
- (id)initWithName:(NSString *)aName filename:(NSString *)aFilename {
self.name = aName;
self.filename = aFilename;
return self;
}
In this class file, I simply set a couple of strings. I load an array with object of this picture class, for example
Picture *image2 = [[Picture alloc] initWithName:#"Apple" filename:#"apple.png"];
[pictureArray addObject: image2];
[image2 release];
Within my viewController, I call this class and assign is as such
Picture *thisPicture = (Picture *)[appDelegate.pictureArray objectAtIndex:0];
view2image.image = [UIImage imageNamed:[NSString stringWithFormat:#"%#", thisPicture.filename]];
The above works fine. The image is set to what ever I put, example, "apple.png". However, when I tried to set this in the - (void) scrollViewDidScroll:(UIScrollView *) method within my viewController, I get a bad exec error and the app crashes.
Yet, if I had an array of filenames (so not storing my class object in the array) and access objectAtIndex:0 in the scrollViewDidScroll - it works fine.
So, this code is OK
nextImageView.image = [UIImage imageNamed: [NSString stringWithFormat:#"%#", [appDelegate.pictureCardsArray objectAtIndex:0]]];
but this crashes
Picture *image3 = (Picture *)[appDelegate.pictureArray objectAtIndex:0];
nextImageView.image = [UIImage imageNamed:[NSString stringWithFormat:#"%#", image3.filename]];
Interestingly though, if I don't try to access the element of image3 (eg image3.filename) it doesn't crash. This is useless though! Also, if I disable the delegate = self for the uiscrollview, then this code works, but none of the scrolling actions are fired. I came across this post (http://stackoverflow.com/questions/1734720/uiscrollview-on-a-uiviewcontroller) when searching for the solution, but cannot see where I might be releasing the viewController early. To be safe, nothing is getting released (yet!)
Hopefully someone might be able to shed some light on it!!
[edit]Just adding in the full class files][/edit]
Picture.h
#import <UIKit/UIKit.h>
#interface Picture : NSObject {
NSString *name;
NSString *filename;
}
#property (nonatomic, copy) NSString *name;
#property (nonatomic, copy) NSString *filename;
- (id)initWithName:(NSString *)aName filename:(NSString *)aFilename;
#end
Picture.m
#import "Picture.h"
#implementation Picture
#synthesize name, filename;
- (id)initWithName:(NSString *)aName filename:(NSString *)aFilename {
self.name = aName;
self.filename = aFilename;
return self;
}
#end

Answer 1

Just for completeness... the solution was as Antwen Van Houdt said - I changed copy to retain and it worked fine.
#import <UIKit/UIKit.h>
#interface Picture : NSObject {
NSString *name;
NSString *filename;
}
#property (nonatomic, retain) NSString *name;
#property (nonatomic, retain) NSString *filename;
- (id)initWithName:(NSString *)aName filename:(NSString *)aFilename;
#end