Given the following `NSSortDescriptor` for strings with Core Data:

```
[NSSortDescriptor sortDescriptorWithKey:@"series" ascending:true selector:@selector(caseInsensitiveCompare:)]

```

The results are correctly ordered alphabetically ascending. However in instances where `series` is `nil`, strings with `nil` values are placed at the top, with non-nil values being sorted thereafter, E.G:

```
[nil, nil, nil, A, B, C, D...]

```

Is there any way to control this behavior? Core Data does not allow for custom selectors. Here's a similar question to mine (not addressing Core Data's limitation, however):

[NSSortDescriptor and nil values](https://stackoverflow.com/questions/2021213/nssortdescriptor-and-nil-values)