5.4 Tracing methods

You can also trace methods (primary and auxiliary) within a generic function. The following example shows how to specify any qualifiers and specializers.

1. Type the following methods into the listener:

   (defmethod foo (x) 
     (print 'there))
    
   (defmethod foo :before ((x integer))
     (print 'hello))
   

2. Next, trace only the second of these methods by typing the following definition spec.

   (trace (method foo :before (integer)))
   

3. Test that the trace has worked by calling the methods in the listener:

   CL-USER 226 > (foo 'x)
    
   THERE 
   THERE
    
   CL-USER 227 > (foo 4)
   0 (METHOD FOO :BEFORE (INTEGER)) > (4)
    
   HELLO 
   0 (METHOD FOO :BEFORE (INTEGER)) < (HELLO)
    
   THERE 
   THERE
    
   CL-USER 228 >