The generic function shared-initialize is used to fill the slots of an instance using initialization arguments and :initform forms when an instance is created, when an instance is re-initialized, when an instance is updated to conform to a redefined class, and when an instance is updated to conform to a different class. It uses standard method combination. It takes the following arguments: the instance to be initialized, a specification of a set of names of slots accessible in that instance, and any number of initialization arguments. The arguments after the first two must form an initialization argument list.
The second argument to shared-initialize may be one of the following:
There is a system-supplied primary method for shared-initialize whose first parameter specializer is the class standard-object. This method behaves as follows on each slot, whether shared or local:
The generic function shared-initialize is called by the system-supplied primary methods for reinitialize-instance, update-instance-for-different-class, update-instance-for-redefined-class, and initialize-instance. Thus, methods can be written for shared-initialize to specify actions that should be taken in all of these contexts.