slot-value object slot-name => value
Arguments and Values:
The function slot-value returns the value of the slot named slot-name in the object. If there is no slot named slot-name, slot-missing is called. If the slot is unbound, slot-unbound is called.
The macro setf can be used with slot-value to change the value of a slot.
(defclass foo () ((a :accessor foo-a :initarg :a :initform 1) (b :accessor foo-b :initarg :b) (c :accessor foo-c :initform 3))) => #<STANDARD-CLASS FOO 244020371> (setq foo1 (make-instance 'foo :a 'one :b 'two)) => #<FOO 36325624> (slot-value foo1 'a) => ONE (slot-value foo1 'b) => TWO (slot-value foo1 'c) => 3 (setf (slot-value foo1 'a) 'uno) => UNO (slot-value foo1 'a) => UNO (defmethod foo-method ((x foo)) (slot-value x 'a)) => #<STANDARD-METHOD FOO-METHOD (FOO) 42720573> (foo-method foo1) => UNO
Affected By: None.
If an attempt is made to read a slot and no slot of the name slot-name exists in the object, slot-missing is called as follows:
(slot-missing (class-of instance) instance slot-name 'slot-value)
(If slot-missing is invoked, its primary value is returned by slot-value.)
If an attempt is made to write a slot and no slot of the name slot-name exists in the object, slot-missing is called as follows:
(slot-missing (class-of instance) instance slot-name 'setf new-value)
(If slot-missing returns in this case, any values are ignored.)
The specific behavior depends on object's metaclass. An error is never signaled if object has metaclass standard-class. An error is always signaled if object has metaclass built-in-class. The consequences are unspecified if object has any other metaclass--an error might or might not be signaled in this situation. Note in particular that the behavior for conditions and structures is not specified.
slot-missing, slot-unbound, with-slots
Although no implementation is required to do so, implementors are strongly encouraged to implement the function slot-value using the function slot-value-using-class described in the Metaobject Protocol.
Implementations may optimize slot-value by compiling it inline.