Java's java.lang.Class class has a getDeclaredFields method which will return all the fields in a given class. Is there something similar for Common Lisp? I came across some helpful functions such as describe, inspect and symbol-plist after reading trying out the instructions in Successful Lisp, Chapter 10 (http://www.psg.com/~dlamkins/sl/chapter10.html). But none of them do what getDeclaredFields does.
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2 Answers
You should use class-slots and/or class-direct-slots (both are from CLOS Metaobject Protocol, MOP). class-slots returns all slots that are present in given class, and class-direct-slots returns all slots are declared in class definition.
Different lisp implementations implement MOP slightly differently; use closer-mop package to have uniform interface to MOP.
Example:
(defclass foo ()
(foo-x))
(finalize-inheritance (find-class 'foo)) ;this is needed to be able to query class slots and other properties. Or, class is automatically finalized when its first instance is created
(class-slots (find-class 'foo))
=> (#<STANDARD-EFFECTIVE-SLOT-DEFINITION FOO-X>)
(slot-definition-name (first (class-slots (find-class 'foo))))
=> FOO-X
Example :
(defun inspect (( object standard-object))
(inspect-rec (class-slots (class-of object)) object) )
(defun inspect-rec (slots o)
( if(atom slots) ()
(let ((sn (slot-definition-name (car slots)))) (cons (list sn '=> ( slot-value o sn) ) ( inspect-rec (cdr slots) o)))))
Comments
I think you're looking for the MetaObject Protocol for CL.
1 Comment
lindes
This link is giving a 404 error. Please "Provide context for links"; down-voting for now, though there's probably something to this answer, and I know there are other resources for learning about the MOP, as it's sometimes called. Happy to re-consider vote with a fresh link AND a bit more info (perhaps info on something specific that approximates
getDeclaredFields).