Common Lisp中的类内省

Question

Java的java.lang.Class类有一个getDeclaredFields方法,它将返回给定类中的所有字段.Common Lisp有类似的东西吗？在阅读了成功的Lisp第10章(http://www.psg.com/~dlamkins/sl/chapter10.html)中的说明之后,我遇到了一些有用的函数,比如describe,inspect和symbol-plist .但是他们都不会像getDeclaredFields那样做.

Answer 1

您应该使用类槽和/或类直接槽(两者都来自CLOS Metaobject Protocol,MOP).class-slots返回给定类中存在的所有槽,而class-direct-slots返回在类定义中声明的所有槽.

不同的lisp实现稍微不同地实现MOP; 使用closer-mop包来实现与MOP的统一接口.

例:

(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

示例:

(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)))))

Answer 2

我认为你正在寻找CL的MetaObject协议.