Apropos

slot-missingStandard Generic Function

    Syntax

    slot-missing class object slot-name operation &optional new-value {result}*

    Method Signatures
    slot-missing (class t) object slot-name
    operation &optional new-value
    Arguments and Values

    class — the class of object.

    object — an object.

    slot-name — a symbol (the name of a would-be slot).

    operation — one of the symbols setf, slot-boundp, slot-makunbound, or slot-value.

    new-value — an object.

    result — an object.

    Description

    The generic function slot-missing is invoked when an attempt is made to access a slot in an object whose metaclass is standard-class and the slot of the name slot-name is not a name of a slot in that class. The default method signals an error.

    The generic function slot-missing is not intended to be called by programmers. Programmers may write methods for it.

    The generic function slot-missing may be called during evaluation of slot-value, (setf slot-value), slot-boundp, and slot-makunbound. For each of these operations the corresponding symbol for the operation argument is slot-value, setf, slot-boundp, and slot-makunbound respectively.

    The optional new-value argument to slot-missing is used when the operation is attempting to set the value of the slot.

    If slot-missing returns, its values will be treated as follows:

    Exceptional Situations

    The default method on slot-missing signals an error of type error.

    See Also

    defclass, slot-exists-p, slot-value

    Notes

    The set of arguments (including the class of the instance) facilitates defining methods on the metaclass for slot-missing.