delete a character from a string Xcode - xcode6

Question

I am using the following code to add a character to a mutable string then put it into a textview from a custom keyboard
- (IBAction) press:(id)sender {
[[UIDevice currentDevice] playInputClick];
if (sender == AEE) {
self.BACK.hidden = NO;
A = #"A";
NSLog(#"sender:%#",sender);
}
if (sender == BEE) {
self.BACK.hidden = NO;
A = #"B";
}
if (sender == CEE) {
self.BACK.hidden = NO;
A = #"C";
}
if (sender == DEE) {
self.BACK.hidden = NO;
A = #"D";
}
if (sender == EEE) {
self.BACK.hidden = NO;
A = #"E";
}
if (sender == EFF) {
self.BACK.hidden = NO;
A = #"F";
}
if (sender == ONE) {
self.BACK.hidden = NO;
A = #"1";
}
if (sender == TWO) {
self.BACK.hidden = NO;
A = #"2";
}
if (sender == THREE) {
self.BACK.hidden = NO;
A = #"3";
}
if (sender == FOUR) {
self.BACK.hidden = NO;
A = #"4";
}
if (sender == FIVE) {
self.BACK.hidden = NO;
A = #"5";
}
if (sender == SIX) {
self.BACK.hidden = NO;
A = #"6";
}
if (sender == SEVEN) {
self.BACK.hidden = NO;
A = #"7";
}
if (sender == EIGHT) {
self.BACK.hidden = NO;
A = #"8";
}
if (sender == NINE) {
self.BACK.hidden = NO;
A = #"9";
}
if (sender == ZERO) {
self.BACK.hidden = NO;
A = #"0";
}
if (display.length <= 7) {
[self.display appendString:A];
DONE.hidden = YES;
}
if (display.length == 8) {
DONE.hidden = NO;
}
else {
[self.display appendString:#""];
}
//**THIS IS WHERE I DELETE CHARATERS**
if (sender == BACK) {
[display deleteCharactersInRange:NSMakeRange([display length]-2, 2)];
NSLog(#"display2:%#", display);
if (self.display.length <1) {
BACK.hidden = YES;
}
if (display.length < 8) {
DONE.hidden = YES;
}
}
you.text = display;
}
When I use the code to delete characters it works fine with for all the characters 1 - 7. Wherever I am if I hit the backspace button it deletes one character. However when I hit the backspace button to delete a character from having 8 characters it deletes two characters. If I change the code to only delete one character like
[display deleteCharactersInRange:NSMakeRange([display length]-1, 1)];
it only deletes one character once. And if I put
[display deleteCharactersInRange:NSMakeRange([display length]-1, 2)];
it does the same thing. But when I put
[display deleteCharactersInRange:NSMakeRange([display length]-2, 1)];
my app crashes and I get an out of bounds error. I have tried using if display =<7 use one the -2,2 code and if display ==8 use the -1,1 code but nothing make it reduce the number of character by one all the time. Does anyone have any suggestions?

Answer 1

I figured out that if I created a separate action to delete and used the following code everything seemed to work ok
(IBAction) Delete:(id)sender{
[[UIDevice currentDevice] playInputClick];
if (sender == BACK) {
if ([display length] > 0) {
[display setString:[display substringToIndex:[display length]-1]];
you.text = display;
}
else {
you.text = display;
//no characters to delete... attempting to do so will result in a crash
}
if (self.display.length <1) {
BACK.hidden = YES;
}
if (display.length < 8) {
DONE.hidden = YES;
}
}