UITextField Should accept number only values

Question

I have UITexfields i want that it should accept only number other shows alert that enter a numeric value. I want that motionSicknessTextFiled should only accept number

Answer 1

I've implemented the snippet which has the features for textField:

1. Check the maximum allowed characters.
2. Check the valid decimal number.
3. Check only numeric numbers.

The code is the UITextField delegate method. Before you use this snippet, you must have these properties:

1. self.maxCharacters
2. self.numeric // Only int characters.
3. self.decimalNumeric // Only numbers and ".", "," (for specific locales, like Russian).

Code:

- (BOOL)textField:(UITextField *) textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    if(self.numeric || self.decimalNumeric)
    {
        NSString *fulltext = [textField.text stringByAppendingString:string];
        NSString *charactersSetString = @"0123456789";

        // For decimal keyboard, allow "dot" and "comma" characters.
        if(self.decimalNumeric) {
            charactersSetString = [charactersSetString stringByAppendingString:@".,"];
        }

        NSCharacterSet *numbersOnly = [NSCharacterSet characterSetWithCharactersInString:charactersSetString];
        NSCharacterSet *characterSetFromTextField = [NSCharacterSet characterSetWithCharactersInString:fulltext];

        // If typed character is out of Set, ignore it.
        BOOL stringIsValid = [numbersOnly isSupersetOfSet:characterSetFromTextField];
        if(!stringIsValid) {
            return NO;
        }

        if(self.decimalNumeric)
        {
            NSString *currentText = [textField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];

            // Change the "," (appears in other locale keyboards, such as russian) key ot "."
            currentText = [currentText stringByReplacingOccurrencesOfString:@"," withString:@"."];

            // Check the statements of decimal value.
            if([fulltext isEqualToString:@"."]) {
                textField.text = @"0.";
                return NO;
            }

            if([fulltext rangeOfString:@".."].location != NSNotFound) {
                textField.text = [fulltext stringByReplacingOccurrencesOfString:@".." withString:@"."];
                return NO;
            }

            // If second dot is typed, ignore it.
            NSArray *dots = [fulltext componentsSeparatedByString:@"."];
            if(dots.count > 2) {
                textField.text = currentText;
                return NO;
            }

            // If first character is zero and second character is > 0, replace first with second. 05 => 5;
            if(fulltext.length == 2) {
                if([[fulltext substringToIndex:1] isEqualToString:@"0"] && ![fulltext isEqualToString:@"0."]) {
                    textField.text = [fulltext substringWithRange:NSMakeRange(1, 1)];
                    return NO;
                }
            }
        }
    }

    // Check the max characters typed.
    NSUInteger oldLength = [textField.text length];
    NSUInteger replacementLength = [string length];
    NSUInteger rangeLength = range.length;

    NSUInteger newLength = oldLength - rangeLength + replacementLength;
    BOOL returnKey = [string rangeOfString: @"\n"].location != NSNotFound;

    return newLength <= _maxCharacters || returnKey;
}

Demo: