Question

I am using:

cleanedDataCellR2C2 =  [cleanedDataCellR2C2 stringByReplacingOccurrencesOfString:@"," withString:@""];

and a whole bunch of similar satements to remove all keyboard characters from a textfield, except the digits…. – (the minus sign), + (the plus sign), as well as 0,1,2,3,4,5,6,7,8, and 9 numbers in a text field. The example above simply converts a comma in an NSString to a null value.

Hate to admit it, but in one project, I’m actually using about 80 statements — one for every keyboard character except those shown above. Thee must be some easier way. What would you suggest to do this job?

Answer 1

The best solution is to not let them enter non-numeric data in the first place, if you can. Are you using a UITextField? If not, ignore the rest of this, but if so:

First, make your view controller is a UITextFieldDelegate, e.g.:

@interface MyViewController : UIViewController <UITextFieldDelegate>

and then later, in viewDidLoad:

self.myTextField.delegate = self;

Second, add a shouldChangeCharacterInRange to only allow the desired characters:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSCharacterSet *nonNumeric = [[NSCharacterSet characterSetWithCharactersInString:@"+-0123456789"] invertedSet];

    if ([string rangeOfCharacterFromSet:nonNumeric].location == NSNotFound)
        return TRUE;
    else
        return FALSE;
}

Third, you might want to change your text field’s keyboard to be for numeric data only, e.g. self.myTextField.keyboardType = UIKeyboardTypeNumbersAndPunctuation or UIKeyboardTypeDecimalPad or something like that.