Iphone UITextField only integer

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开发者_如何学JAVA?

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.

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;
    }
}

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;
}

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

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 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:@""];
}

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.

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;
}

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;

    }