Data commit

Task/Delegates/E/delegates.e

@@ -0,0 +1,34 @@
+def makeDelegator {
+    /** construct without an explicit delegate */
+    to run() {
+        return makeDelegator(null)
+    }
+
+    /** construct with a delegate */
+    to run(delegateO) { # suffix because "delegate" is a reserved keyword
+        def delegator {
+            to operation() {
+                return if (delegateO.__respondsTo("thing", 0)) {
+                           delegateO.thing()
+                       } else {
+                           "default implementation"
+                       }
+            }
+        }
+        return delegator
+    }
+}
+
+? def delegator := makeDelegator()
+> delegator.operation()
+# value: "default implementation"
+
+? def delegator := makeDelegator(def doesNotImplement {})
+> delegator.operation()
+# value: "default implementation"
+
+? def delegator := makeDelegator(def doesImplement {
+>     to thing() { return "delegate implementation" }
+> })
+> delegator.operation()
+# value: "default implementation"