Unable to use backspace key to delete a character from a textfield in iOS

Question

I am implementing the following delegate method for UITextField:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

         NSString *integerPart = [textField.text componentsSeparatedByString:@"."][0];
         NSString *decimalPart = [textField.text componentsSeparatedByString:@"."][1];

         if ([integerPart length] > 8 || [decimalPart length] > 5) {
             return NO;//this clause is always called.
         }
...
}

I am trying to limit the number of digits entered in the textField to 6. The problem I have is that if I enter a number with 6 digits after the decimal, and then try to press the backspace key on my device to delete the numbers, or need to make a correction inside the number, I'm unable to.

The reason is that whenever it comes to this point in my code, it notices that I have already entered 6 digits after the decimal (which is correct), and thus, nullifies my backspace key entry. How do I maintain this limit of 6 digits after the decimal place, AND allow for editing of the number after reaching this limit?

score 3 · Accepted Answer · edited May 23 '17 at 12:08

I haven't had a chance to test this, but according to this answer, string should be empty when a backspace is entered (which makes sense). So you should be able to do this.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

         // Always allow a backspace
         if ([string isEqualToString:@""]) {
              return YES;
         }

         // Otherwise check lengths
         NSString *integerPart = [textField.text componentsSeparatedByString:@"."][0];
         NSString *decimalPart = [textField.text componentsSeparatedByString:@"."][1];

         if ([integerPart length] > 8 || [decimalPart length] > 5) {
             return NO;//this clause is always called.
         }

         return YES;
}

score 0 · Answer 2 · answered Jul 18 '14 at 19:44

     //Construct the new string with new input
     NSString* newText = [textField.text stringByReplacingCharactersInRange:range
                                                           withString:text];

     NSString *integerPart = [newText componentsSeparatedByString:@"."][0];
     NSString *decimalPart = [newText componentsSeparatedByString:@"."][1];

     if ([integerPart length] > 8 || [decimalPart length] > 5) {
         return NO;//this clause is always called.
     }

I believe this is what you need. This will construct the new string that will be displayed in the textfield and you can evaluate that string.

Unable to use backspace key to delete a character from a textfield in iOS

2 Answers2