NSString stringWithFormat: with C array?

Question

Hi,

I'm writing a program that calculates the Jacobi algorithm. It's written in Objective-C since it runs on a Mac, but the majority is written in standard C. I'm using a two-dimensional C array and an NSArray containing 5 NSTextField labels.

The following code yields an EXC_BAD_ACCESS error:

for ( int i = 0; i < 5; i++ ) {
     NSString *resultString = [NSString stringWithFormat:@"%g", matrix[i][i] ];
     [[resultLabels objectAtIndex:i] setStringValue:resultString]; // error line
}

Any help?

EDIT

Here's where I init resultLabels:

resultLabels = [[NSArray alloc] initWithObjects:result11, result22, result33, result44, result55, nil];

Answer 1

If you get the error on that line, then either resultsLabels is released, or the object at i is.

Answer 2

Most likely, you are referencing an object that has been released. Is your NSArray or objectAtIndex: nil at that point? Can you show the lines where you instantiate these objects?

Answer 3

This isn't the source of your crasher, but the %g format code is for doubles not ints; you want %d.

The items in the array would be automatically retained by the array (objects in Foundation collections are always retained by the collection), so you shouldn't need to send them extra -retain messages. So it would seem as though resultLabels may be getting released somewhere before the crash occurs.