Obj-C - NSString to int

I'm making this function that takes a string input, converts it to an int, and finds the binary equivalent. It was working an hour ago, but after i tried tinkering with a different keypad, and then going back, it no longer works:

 - (void)convertToBinary:(NSString *)tf
    {
      NSString *result = @"";
      NSLog(@"-- %@", tf); //successfully prints
      [tf retain];
      if ([tf isKindOfClass:[NSString class]]){
        NSLog(@"tf is NSString"); //THIS PRINTS SO TF IS CONFIRMED TO BE NSSTRING
       }
      int dec = [tf intValue]; //BREAKS HERE...!

      if (!dec){
        [binaryOutput setText:@"Sorry, invalid input!"];
        } else {
              ...
        }

}

I know that to convert an NSString to an int, i just need to do int dec = [someString intValue] yet that isn't working. The error i'm getting is EXEC_BAD_ACCESS

Any help please?

EDIT

I just made a small command-line project:

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool all开发者_JAVA百科oc] init];

    // insert code here...
    NSString *t = @"123";
    int d = [t intValue];
    NSLog(@"Hello, %@", d);
    [pool drain];
    return 0;
}

and the EXEC_BAD_ACCESS still persists for such a simple program! What's the problem here?

You should be using "%d" when printing integers. Change the line to:

NSLog(@"Hello, %d", d); 

EXEC_BAD_ACCESS usually fires when there is a memory leak, check that tf is not null or released. You can write NSLog(@"%@", tf); at the beginning of the method to check that.

As edo42 it's probably related to a null/released string. See "EXC_BAD_ACCESS signal received" for lots of information about that error message, and how to debug using NSZombieEnabled.

Instruments.app with the Zombies instrument might help to uncover the crash. Also try a "Build and Analyze" run.