Phone formatter

.m

self.mask = @"111-222-3333";

- (BOOL)textField:(UITextField *)textField
shouldChangeCharactersInRange:(NSRange)range
replacementString:(NSString *)string
{
    if (textField.tag == 5) 
    {
        
        //If the length of used entered text is equals to mask length the user input must be cancelled 
        if ([textField.text length] == [self.mask length]) {
            if(! [string isEqualToString:@""])
                return NO;
            else 
                return YES;
        }
        //If the user has started typing text on UITextField the formatting method must be called
        else if ([textField.text length] || range.location == 0) 
        {
            if (string) 
            {
                if(! [string isEqualToString:@""]) 
                {
                    [self formatInput:textField string:string range:range];
                    return NO;
                }
                return YES;
            }
            return YES;
        }
        
        return NO;
    } 
    else if (textField.tag == NAMEFIELD_TAG) 
    {
        if ([textField.text length] >= MAXLENGTH) 
        {
            textField.text = [textField.text substringToIndex:MAXLENGTH-1];
            return NO;
        }
        return YES;
    } else {
        return YES;
    }
}

//This method is responsible for add mask characters properly
- (void)formatInput:(UITextField*)aTextField string:(NSString*)aString range:(NSRange)aRange
{
    //Copying the contents of UITextField to an variable to add new chars later
    NSString* value = aTextField.text;
    
    NSString* formattedValue = value;
    
    //Make sure to retrieve the newly entered char on UITextField
    aRange.length = 1;
    
    NSString* _mask = [self.mask substringWithRange:aRange];
    
    //Checking if there's a char mask at current position of cursor
    if (_mask != nil) {
        NSString *regex = @"[0-9]*";
        
        NSPredicate *regextest = [NSPredicate
                                  predicateWithFormat:@"SELF MATCHES %@", regex];
        //Checking if the character at this position isn't a digit 
        if (! [regextest evaluateWithObject:_mask]) {
            //If the character at current position is a special char this char must be appended to the user entered text
            formattedValue = [formattedValue stringByAppendingString:_mask];
        } 
        
        if (aRange.location + 1 < [self.mask length]) {
            _mask =  [self.mask substringWithRange:NSMakeRange(aRange.location + 1, 1)];
            if([_mask isEqualToString:@" "])
                formattedValue = [formattedValue stringByAppendingString:_mask];
        }
    }
    //Adding the user entered character
    formattedValue = [formattedValue stringByAppendingString:aString];
    
    //Refreshing UITextField value       
    aTextField.text = formattedValue;
}