Question

i have a problem passing a string to another UIViewController and then open this UIViewController, this is what i do:

.h

#import <UIKit/UIKit.h>

@interface BroswerViewController : UIViewController

@property (retain, nonatomic) IBOutlet UIWebView *myBrowserView;
@property (nonatomic, retain) NSString * myString;
@end

.m

@implementation BroswerViewController
@synthesize myBrowserView;
@synthesize myString;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
    // Custom initialization

}
return self;
}

- (void)viewWillAppear:(BOOL)animated {

myString = [myString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"http://mywebsite/%@",myString]];
NSLog(@"%@",url);
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[myBrowserView loadRequest:request];

}

class where i call it:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
if (!self.myBroserViewController) {
    self.myBroserViewController = [[[BroswerViewController alloc] initWithNibName:@"BroswerViewController" bundle:nil] autorelease];
}

[self.myBroserViewController setMyString:[NSString stringWithString:[stringArray objectAtIndex:indexPath.row]]];
[self.navigationController pushViewController:self.myBroserViewController animated:YES];
}

ok, so i pass a string to the BrowseViewController class, and then open the browseviewcontroller class and open the url with the string i have passed, and the first time work always, then i return back and pass another string and open the view and the second time works random, and the third time never, and i always receive a EXC_BAD_ACCESS on the line

@synthesize myString;

i don’t know what i wrong…

Answer 1

I would add a couple of pointers to @Phillip Mills answer.

-On your init you should set myString to nil. This ensures that if it is released before being set somewhere else, it won’t crash. Including if you use the setter which performs a release on it (you can release a nil reference).

-On your dealloc, you should release myString (unless you are using ARC).

-When you set it in viewWillAppear, you either need to do:

self.myString = [self.myString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

or

NSString *temp = myString;
[myString release];
myString = [[temp stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding] retain];

they both accomplish the same thing. Using self is easier though.

-Finally, I would use copy instead of retain unless you have a very specific reason to use retain. This ensures something else doesn’t change it on you.