When my UIViewController accesses an NSArray in my AppDelegate from an IBAction it crashes the program - iphone-sdk-3.0

Question

I have a couple UIViewControllers that I am trying to access an array inside my AppDelegate. When I use an IBAction UIButton and in that method I access my AppDelegate my program dies silently. Nothing in output or the debugger, it just stops. If I run it several times I can see that it is failing to access the array properly.
To investigate this problem I created a very basic app.
In my AppDelegate.h I declared and set properties for the array
#import <UIKit/UIKit.h>
#class MyViewController;
#interface MyAppDelegate : NSObject <UIApplicationDelegate> {
UIWindow *window;
MyViewController *viewController;
NSArray *images;
}
#property (nonatomic, retain) NSArray *images;
#property (nonatomic, retain) IBOutlet UIWindow *window;
#property (nonatomic, retain) IBOutlet MyViewController *viewController;`
In the AppDelegate.m I synthesised and initialized the NSArray (Also made sure the images were added to the Resources folder).
#synthesize images;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
images = [NSArray arrayWithObjects:
[[NSBundle mainBundle] pathForResource:#"bamboo_nw" ofType:#"jpg"],
.....
nil];
NSLog(#"init images size:%i",[images count]);
[window addSubview:viewController.view];
[window makeKeyAndVisible];
return YES;
}
In my UIViewController.h I added class, imported header file, declared, and set properties for my AppDelegate pointer.
#import <UIKit/UIKit.h>
#import "MyAppDelegate.h"
#class MyAppDelegate;
#interface MyViewController : UIViewController {
MyAppDelegate *mainDelegate;
IBOutlet UIButton mybutton;
}
#property (nonatomic, retain) MyAppDelegate mainDelegate;
#property (nonatomic, retain) UIButton *mybutton;
-(IBAction) doSomething;`
In my UIViewController.m I synthesize and assign my AppDelegate. I set up an IBAction that will log the same count of the NSArray from the AppDelegate.
#import "MyViewController.h"
#import "MyAppDelegate.h"
#implementation MyViewController
#synthesize mybutton;
- (void)viewDidLoad {
mainDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
NSLog(#"vdl images size:%i",[mainDelegate.images count]);
[super viewDidLoad];
}
-(IBAction) doSomething {
NSLog(#"ds images size:%i",[mainDelegate.images count]);
}
I print the size of the NSArray in the AppDelegate when I create it, in the ViewController when I first assign my AppDelegate pointer, and then as a result of my IBAction.
I find that everytime I hit the button the program dies. On the third time I hit the button, I saw that it ran my IBAction but printed my array size as 1 instead of 8. Am I missing something? Also, why don't I get stack traces or anything, the debugger just dies silently?
Thanks in advance for any help!
Debugger Console output for 3 runs:
[Session started at 2010-05-10 06:21:32 -0700.]
2010-05-10 06:21:44.865 My[59695:207] init images size:8
2010-05-10 06:21:47.246 My[59695:207] vdl images size:8
[Session started at 2010-05-10 06:22:15 -0700.]
2010-05-10 06:22:18.920 My[59704:207] init images size:8
2010-05-10 06:22:19.043 My[59704:207] vdl images size:8
[Session started at 2010-05-10 06:22:23 -0700.]
2010-05-10 06:22:25.966 My[59707:207] init images size:8
2010-05-10 06:22:26.017 My[59707:207] vdl images size:8
2010-05-10 06:22:27.814 My[59707:207] ds images size:1

Answer 1

You need to use self.images as your lvalue in application:DidFinishLaunchingWithOptions:, to wit:
#synthesize images;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions(NSDictionary *)launchOptions {
self.images = [NSArray arrayWithObjects:
[[NSBundle mainBundle] pathForResource:#"bamboo_nw" ofType:#"jpg"],
.....
nil];
NSLog(#"init images size:%i",[images count]);
[window addSubview:viewController.view];
[window makeKeyAndVisible];
return YES;
}
When you use the ivar images without the self, you are giving up the goodness of the automatic retention that you set up when you created the #property.