What does "out of scope" mean in Xcode debugger (for iPhone)?

Question

I'm loading a detailed view of an article when clicking on a row in a UITableView. When clicked, it loads the object with the data and I pass that object to the next controller being pushed on the stack. However, when I do this:

- (void)showArticle
{
    [aTitle setText:[[self article] title]];
    [aTitle setBackgroundColor:[UIColor clearColor]];
    [[self view] addSubview:aTitle];

    [aCategory setText:[[self article] category]];
    [aCategory setBackgroundColor:[UIColor clearColor]];
    [[self view] addSubview:aCategory];

    [aAuthors setText:[[self article] authors]];
    [aAuthors setBackgroundColor:[UIColor clearColor]];
    [[self view] addSubview:aAuthors];
}

The title shows up fine, but the category and authors aren't showing up. When I debug, I'm getting "out of scope" when I look at the values of the category/authors. The article object is being @synthesized and I've checked it and it has the right data.

Any ideas? Does that mean that a method is private or something?

Thanks!

Answer 1

It means the debugger couldn't see it when it tried to query its value. Sometimes that means the variable really is out of scope in the sense that it belongs to a C block you are not in. But there is a glitch where sometimes Objective-C objects, particularly NSStrings appear out of scope when they are really perfectly OK. It's almost never (in my experience) a programming error.

Try right clicking the variable and selecting "print description to console" if you need to see what the real value is.

Answer 2

After a longtime to workaround this issue, you should use an object when assign to userData event NSString like this:

@interface callBackData
 @NSString *text;
 @NSInteger point;
@end

use it:

callBackData *data = [[callBackData alloc] init];
data.text=[NSString stringWithString:@"something"];
something.userData = data;

And you'll be always OK.

Pls remember do not assign directly NSString for userData, because of sometime it will be out of scope without reason