Iphone UITextField only integer - iphone

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;
}
}

Answer 3

Try this: It will stop user to enter any character other then numbers
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSCharacterSet *nonNumberSet = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];
if ([string rangeOfCharacterFromSet:nonNumberSet].location != NSNotFound)
{
return NO;
}
return YES;
}

Answer 4

http://rosettacode.org/wiki/Determine_if_a_string_is_numeric#Objective-C
Or you could ensure that only the numeric keyboard appears when the focus comes on the field

Answer 5

To only allow for numeric input:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
return [string isEqualToString:#""] ||
([string stringByTrimmingCharactersInSet:
[[NSCharacterSet decimalDigitCharacterSet] invertedSet]].length > 0);
}
To test for an integer:
- (BOOL)isNumeric:(NSString *)input {
for (int i = 0; i < [input length]; i++) {
char c = [input characterAtIndex:i];
// Allow a leading '-' for negative integers
if (!((c == '-' && i == 0) || (c >= '0' && c <= '9'))) {
return NO;
}
}
return YES;
}

Answer 6

Answer by #devsan is incorrect. If a user pastes anything with a a number such as "1abc" her code would break
It should be (allow replacement only if all the chars are digits):
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSCharacterSet *nonNumberSet = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];
return ([string stringByTrimmingCharactersInSet:nonNumberSet].length == string.length) || [string isEqualToString:#""];
}

Answer 7

You could also use UITextFieldDelegate method
textField:shouldChangeCharactersInRange:replacementString:
to live check that each time the user press a key, it is a simple digit, so that he/she knows that only int value is to be entered in the field.

Answer 8

Want to allow negative numbers as well?
Elaborating on davsan's answer, here is a solution that supports entering negative as well as positive numbers, and disallows anything else.
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSCharacterSet *nonNumberSet = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];
return ([string stringByTrimmingCharactersInSet:nonNumberSet].length > 0) || [string isEqualToString:#""] || ([textField.text isEqualToString:#""] && [string isEqualToString:#"-"]);
return YES;
}

Answer 9

This code is work with localisation too .
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
if([string isEqualToString:#""]) return YES;
NSCharacterSet *characterSet = nil;
characterSet = [NSCharacterSet decimalDigitCharacterSet];
NSRange location = [string rangeOfCharacterFromSet:characterSet];
return (location.location != NSNotFound);
if(characterSet == nil) return YES;
return YES;
}