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?

Solution 1

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

Solution 2

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.

Solution 3

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;
    }
}

Solution 4

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;
}

Solution 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;
}

View more solutions

Comments

[GarethPrice]

This does not work if the first character typed is a letter. If a number is typed first, then a letter is typed it works, however.

[Shoerob]

Relying on the numeric keyboard isn't safe since the user could potentially paste string data into the field instead of even using the keyboard.

[andershqst]

To enable delete: return ([string stringByTrimmingCharactersInSet:nonNumberSet].length > 0) || [string isEqualToString:@""];

[endo.anaconda]

last answer is more accourate

[mbogh]

Only problem is if a user paste in a string e.g. 1n1a, stringByTrimmingCharactersInSet: will only remove from start and end of the string. Do something like: NSRegularExpression *numbersOnly = [NSRegularExpression regularExpressionWithPattern:@"[0-9]+" options:NSRegularExpressionCaseInsensitive error:&error]; NSInteger numberOfMatches = [numbersOnly numberOfMatchesInString:string options:0 range:NSMakeRange(0, string.length)]; if (numberOfMatches != 1 && string.length != 0) { shouldChange = NO; }

[mah]

An answer was provided and accepted 2 years ago. Please do not answer such old questions which have already been answered unless you have something substantive to add.

[Yaroslav]

What does your answer adds to the previous ones? Why it is valuable and you think should be an answer? There are already several high upvoted answers to this question, why your is different?

[Christian Loncle]

this was a very quick solution to implement. don't forget to add the textField delegate to the .h file

[septerr]

@mbogh 's comment should be the answer.

[Jason]

Alternatively, you could change the second line to return [string stringByTrimmingCharactersInSet:numbers].length == string.length;