Why is my NSRange always 0?

Question

I want to implement a delete key for my calculator app. My pseudocode for this was:

foo = length of current number
bar = length of current number-1

current number = current number with character at index (foo-bar) removed

To do this in objective-c I have tried to implement this using the NSRange function as well as the StringbyappendingString method:

- (IBAction)DelPressed {
if ([self.display.text length] >=2)
{

    int len = [self.display.text length];//Length of entire display

    //Add to the brainlong printing out the length of the entire display
    self.brainlog.text = [NSString stringWithFormat:@"Len is %g",len];

    int le  = ([self.display.text length]-1);//Length of entire display - 1
    NSString *lestring = [NSString stringWithFormat:@"LE is %g",le];

    //Add to the brainlog printing out the length of the display -1
    self.brainlog.text = [self.brainlog.text stringByAppendingString:lestring];    

    NSRange range = NSMakeRange(le, len);//range only includes the last character

    self.display.text = [self.display.text stringByReplacingCharactersInRange:range withString:@" "];//Replace the last character with whitespace
}

The output to brainlog (ie the length of both le and len) is:

Len is -1.99164 Le is -1.99164

Hard to see, but here's an image of the number I input to the calculator using the iOS simulator:

I have tried to change the value of le (ie making it the length of the display -3 or -5 etc) and both le and len are still the same.

I have also tried to make le in reference to len:

    int len = [self.display.text length];//Length of entire display
    //Add to the brainlong printing out the length of the entire display
    self.brainlog.text = [NSString stringWithFormat:@"Len is %g",len];


    int le = len-1;

But the values of the two are still the same. How can I use NSRange to delete the last character of the display?

Edit: Using Dustin's fix, I now have reduced a rather lengthy function into 6 lines of code:

    -(IBAction)DelPressed{
    if ([self.display.text length] >=2)
    {
         self.display.text = [self.display.text substringToIndes:[self.display.text length] -1];
    }
 }

Kookaburra

%g is also the format specifier for double types, try using %d for int types. – Phenix

What exactly is brainlog? Maybe I'm missing something, but it seems like the real question here has nothing to do with NSRange but instead should be about how on earth you're storing the length of a string as an int and ending up with a negative float instead. Have you tried using NSLog(@"len is %d", len) to verify the value of len? – Frink

'brainlog' is just another 'UILabel' that logs the operators that have been pressed as well as the digits. In this case I am using it as a print statement to see what is going wrong with my method. I have tried the NSlog way and have gotten the same result, always a float of some sort... – Kookaburra

Have you tried it with the proper format specifier, as adc mentioned above (i.e. %d instead of %g)? – Frink

The %g was causing an issue but I have update my answer with an easier way I found using Dustin's method – Kookaburra

Answer 1

Use substring instead; it's much better if all you want to do is remove the last character.

More specifically, substringToIndex(/*length-1*/)

Check this reference out if you need to do other things with strings

Taeniafuge