use new syntax!
```ruby
has_one :detail, class_name: 'UserDetail', dependent: :destroy
```

anyway, do you think to use ```destroy``` to remove user?
this method issues DELETE query. I prefer to use UPDATE ```deleted_at``` column.
In fact, I planed to introduce https://github.com/radar/paranoia or https://github.com/joelteon/rails4_acts_as_paranoid .