remove data sent to UILabel - objective-c

Question

I am creating a calculator app that has a backspace button just incase the user accidentally typed in a number. Is there a way to remove the last thing that was sent to the UILabel?
sure, I am adding my code to show what I am currently doing,
- (IBAction)digitPressed:(UIButton *)sender {
NSString *digit = sender.currentTitle;
if ([digit isEqualToString:#"."] && !_decimalPressed){
self.display.text = [self.display.text stringByAppendingString:digit];
self.historyDisplay.text = [self.display.text stringByAppendingString:digit];
self.decimalPressed = YES;
}
else if (!_isUserInTheMiddleOfEnteringANumber){
self.display.text = digit;
self.historyDisplay.text = digit;
self.isUserInTheMiddleOfEnteringANumber = YES;
}
else if (![digit isEqualToString:#"."]){
self.display.text = [self.display.text stringByAppendingString:digit];
self.historyDisplay.text = [self.display.text stringByAppendingString:digit];
}
}
This how I am trying to get delete the last element
- (IBAction)backSpace:(id)sender {
}

Answer 1

Just remove the last character from the string set inside your label. Example code:
int numChars = myLabel.text.length;
NSString* truncatedString = [myLabel.text substringToIndex:(numChars - 1)];
mLabel.text = truncatedString;

Answer 2

NSMutableString * stringToModify = [[NSMutableString alloc] initWithString: self.display.text];
if(stringToModify && ([stringToModify length] > 0))
{
[stringToModify deleteCharactersInRange: NSMakeRange([stringToModify length] - 1, 1)];
self.display.text = stringToModify;
[stringToModify release]; // if and only if NOT using ARC
}

Answer 3

- (IBAction)backPressed:(id)sender {
self.display.text=[self.display.text substringToIndex:[self.display.text length] -1];
if ([self.display.text isEqualToString:#""] || [self.display.text isEqualToString:#"-"]){
self.display.text = #"0";
self.userIsInTheMiddleOfEnteringANumber=NO;
}
}
Added in some common logic into the code. If you reach the last number and back space again, it will return the display text as 0. Since it's a calculator, assuming you have created the negative sign ( +/- ), if you are left with -, you will want to delete it and place it with 0 as well. Therefore if everything is relinquish back to 0, you will want to set your userIsInTheMiddleOfEnteringANumber to NO as well.