iPhone memory management, EXC_BAD_ACCESS NSString between views - iphone

Question

I have some problems with memory management, I think my problem is the assignment, and object releases. I want to assign a NSString (userID) value to another NSString in other view (user_id).
MainViewController.h
#import "OnlineCheckViewController.h"
#interface MainViewController : UIViewController
{
NSString *userID;
}
#end
MainViewController.m
#import "MainViewController.h"
- (IBAction)OnlineCheck:(id)sender
{
OnlineCheckViewController *controller = [[OnlineCheckViewController alloc] initWithNibName:#"OnlineCheckViewController" bundle:nil];
controller.delegate = self;
controller.user_id = userID;
controller.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
[self presentModalViewController:controller animated:YES];
[controller release];
}
- (void)viewDidUnload
{
userID = nil;
[super viewDidUnload];
}
- (void)dealloc
{
[userID release];
[super dealloc];
}
OnlineCheckViewController.h
#import <UIKit/UIKit.h>
#import "OnlineCheckResultsViewController.h"
#protocol OnlineCheckViewControllerDelegate;
#interface OnlineCheckViewController : UIViewController
<OnlineCheckResultsViewControllerDelegate>
{
NSString *user_id;
}
#property (nonatomic, assign) id <OnlineCheckViewControllerDelegate> delegate;
#property (nonatomic, retain) NSString *user_id;
#end
OnlineCheckViewController.m
#import "OnlineCheckViewController.h"
#synthesize user_id;
#synthesize delegate=_delegate;
- (void)dealloc
{
[user_id release];
[super dealloc];
}
- (void)viewDidUnload
{
[self setUser_id:nil];
[super viewDidUnload];
}
Thanks!

Answer 1

#interface MainViewController : UIViewController
{
NSString *userID;
}
I'm going to bet that this is your problem. Note that when you create the property "user_id", you specify "retain". Retain makes sure that the processor doesn't release the string until you tell it to.
An NSString is automatically set to auto release. If you plan to keep the value in the non property NSString (userID) then you need to call [userID retain]; after you set the value of it.
I'm guessing that you never retained userID and when you try to set user_id to it, it calls the error or more likely, it throws the error because you release it in dealloc.

Answer 2

Thanks to all your answers.
I have resolved this issue.
In MainViewController.h
I have added userID IBOutlet
#property (nonatomic, retain) IBOutlet NSString *userID;
In MainViewController.m
#synthesize userID;
- (IBAction)OnlineCheck:(id)sender
{
controller.user_id = self.userID;
}
- (void)viewDidUnload
{
self.userID = nil;
}
- (void)dealloc
{
[userID release];
}
In OnlineCheckViewController.h
Changed to assign
#property (nonatomic, assign) NSString *user_id;
In OnlineCheckViewController.m
- (void)dealloc
{
// removed
// [user_id release];
}
- (void)viewDidUnload
{
// removed
// [self setUser_id:nil];
}

Answer 3

Try this code
- (IBAction)OnlineCheck:(id)sender
{
    OnlineCheckViewController *controller = [[OnlineCheckViewController alloc] initWithNibName:#"OnlineCheckViewController" bundle:nil];
    controller.delegate = self;
    controller.user_id = userID;
[controller.user_id retain];
    controller.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
    [self presentModalViewController:controller animated:YES];
    [controller release];
}
i think this may solve your problem...