Instances of Metaclass, such as OrderedCollection class, Process class, Magnitude class, etc., and instances of instances of Metaclass, such as OrderedCollection, Process, Magnitude, etc., are considered as special objects because each of these objects is unique in the image. That is, there is exactly one instance of Metaclass with the name Dictionary (also known as Dictionary class), and there is only one instance of Dictionary class (also known as Dictionary) in an image.

The uniqueness of these objects can be illustrated by the following example. Suppose there are two objects, A and B, each containing a reference (directly or indirectly) to Dictionary class. After unloading objects A and B and loading them back into the image (call the newly loaded objects 'A' and 'B'), 'A' and 'B' should not be referencing a different Dictionary class than the one already existing in the image; objects 'A' and 'B' should still reference the identical Dictionary class that was in the image before and after A and B were unloaded and reloaded. Thus, these objects make use of dumping and loading replacement (see Combining dumping and loading replacement). They are replaced by an intermediate representation which rebinds to the appropriate object (class or metaclass) in the image where loading is performed.

In order to unload instances of Metaclass and instances of instances of Metaclass as non-special objects (that is, no replacement performed), the ObjectDumper must be explicitly set to handle these instances as ordinary objects. ObjectDumper instance method classesTreatedAsObjects: will override its default setting and unload the specified classes as objects. The following example shows how you can unload the class ObjectSwapper as an object.