UITextField phone string format

UITextField phone string format

_textField.delegate = self (UITextFieldDelegate)

- (NSMutableString *)filteredPhoneStringFromString:(NSString *)string withFilter:(NSString *)filter
{
    NSUInteger onOriginal = 0, onFilter = 0, onOutput = 0;
    char outputString[([filter length])];
    BOOL done = NO;
    
    while(onFilter < [filter length] && !done)
    {
        char filterChar = [filter characterAtIndex:onFilter];
        char originalChar = onOriginal >= string.length ? '\0' : [string characterAtIndex:onOriginal];
        switch (filterChar) {
            case '#':
                if(originalChar=='\0')
                {
                    // We have no more input numbers for the filter.  We're done.
                    done = YES;
                    break;
                }
                if(isdigit(originalChar))
                {
                    outputString[onOutput] = originalChar;
                    onOriginal++;
                    onFilter++;
                    onOutput++;
                }
                else
                {
                    onOriginal++;
                }
                break;
            default:
                // Any other character will automatically be inserted for the user as they type (spaces, - etc..) or
                //  deleted as they delete if there are more numbers to come.
                outputString[onOutput] = filterChar;
                onOutput++;
                onFilter++;
                if(originalChar == filterChar)
                    onOriginal++;
                break;
        }
    }
    outputString[onOutput] = '\0'; // Cap the output string
    return [[NSString stringWithUTF8String:outputString] copy];
}


- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    
    NSString *filter = @"# (###) ### ## ##";
    
    if(!filter) return YES; // No filter provided, allow anything
    
    NSString *changedString = [textField.text stringByReplacingCharactersInRange:range withString:string];
    
    if(range.length == 1 && // Only do for single deletes
       string.length < range.length &&
       [[textField.text substringWithRange:range] rangeOfCharacterFromSet:[NSCharacterSet characterSetWithCharactersInString:@"0123456789"]].location == NSNotFound)
    {
        // Something was deleted.  Delete past the previous number
        NSInteger location = changedString.length-1;
        if(location > 0)
        {
            for(; location > 0; location--)
            {
                if(isdigit([changedString characterAtIndex:location]))
                {
                    break;
                }
            }
            changedString = [changedString substringToIndex:location];
        }
    }
    
    textField.text = [self filteredPhoneStringFromString:changedString withFilter:filter];
    
    return NO;
}