Reading string from array then changing string and outputting new result

Question

I am trying to grab a string in my array, change nth letter in the string to a ?, then print the result in a textfield. The problem is my NSMutableArray is being stored into a UIPickerView and I think it would be best just to read the string from the PickerView then change the nth char and print the result. I am struggling with how to grab the string from the picker and change the nth letter.

    - (UIView *)viewForRow:(NSInteger)row forComponent:(NSInteger)component
    {
    if (row == 0 ) {
     NSString *originalStringTwo = @"%@", *arrayDictionary;
    NSRange two = [originalStringTwo rangeOfString:@"2"];
    NSString *newStringTwo = [originalStringTwo stringByReplacingCharactersInRange:two        withString:@"?"];

    _resultLabel.text = newStringTwo;
    }


    if (row == 1 ) {
    NSString *originalStringThree = @"%@", *arrayDictionary;
    NSRange three = [originalStringThree rangeOfString:@"3"];
    NSString *newStringThree = [originalStringThreestringByReplacingCharactersInRange:three withString:@"?"];

    _resultLabel.text = newStringThree;
    }

    if ( row == 2 ) {
    NSString *originalStringFour = @"%@", *arrayDictionary;
    NSRange four = [originalStringFour rangeOfString:@"4"];
    NSString *newStringFour = [originalStringFour stringByReplacingCharactersInRange:four withString:@"?"];

   _resultLabel.text = newStringFour;
    }
    return 0;
}

Answer 1

That's not how you create an NSRange. Use NSMakeRange instead.

// Range from index 1 with length 1, eg. 2nd character:
NSRange two = NSMakeRange(2, 1);
NSString *newStringTwo = [originalStringTwo stringByReplacingCharactersInRange:two
                          withString:@"?"];

Note, that it's never a good idea to grab any data from a GUI element (except user input). What if the text field applies custom formatting?

You should keep your data in your array and use that.