1 files changed, 30 insertions, 0 deletions
diff --git a/src/core/unit.lisp b/src/core/unit.lisp
new file mode 100644
index 0000000..20e05e2
--- /dev/null
+++ b/src/core/unit.lisp
@@ -0,0 +1,30 @@
+;;;; units/unit.lisp
+
+(in-package #:wheelwork)
+
+(defclass/std unit ()
+  ((cached-application  :a)
+   (container :with :a)))
+
+(defmethod (setf closer-mop:slot-value-using-class) :after
+    (newval class (unit unit) slot)
+  (case (closer-mop:slot-definition-name slot)
+    (container
+     (setf (cached-application unit) nil))))
+
+
+(defun app-of-unit (unit)
+  "Returns the APPLICATION instance, if any, of which this UNIT is a
+part. NIL indicates that the unit has not been added to any container
+in this application."
+  (or (cached-application unit) 
+      (setf (cached-application unit) 
+            (labels ((rec (u)
+                       (when-let (c (unit-container u))
+                         (etypecase c
+                           (application c)
+                           (unit (rec c))
+                           (null nil)))))
+              (rec unit)))))
+
+