Iphone UITextField only integer

Question

I have a UITextField in my IB and I want to check out if the user entered only numbers (no char)and get the integer value.

I get the integer value of the UITextField like that :

int integer = [myUITexrtField.text intValue];

When I put a character ( , ; . ) it return me 0 and I don't know how to detect that it is not only numbers.

How can I do?

Answer 1

Implementing shouldChangeCharactersInRange method as below does not allow the user input non-numeric characters.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string { 
    NSCharacterSet *nonNumberSet = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];
    return ([string stringByTrimmingCharactersInSet:nonNumberSet].length > 0) || [string isEqualToString:@""];
}

This returns YES if the string is numeric, NO otherwise. the [string isEqualToString@""] is to support the backspace key to delete.

I love this approach because it's clean.

Answer 2

Be sure to set your text field delegate

Use the following function to ensure user can type in numbers only:

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

    NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
    [numberFormatter setNumberStyle:NSNumberFormatterDecimalStyle];

    NSNumber* candidateNumber;

    NSString* candidateString = [textField.text stringByReplacingCharactersInRange:range withString:string];

    range = NSMakeRange(0, [candidateString length]);

    [numberFormatter getObjectValue:&candidateNumber forString:candidateString range:&range error:nil];

    if (([candidateString length] > 0) && (candidateNumber == nil || range.length < [candidateString length])) {

        return NO;
    }
    else 
    {
        return YES;
    }
}