2016 Update

Task/Delegates/Elena/delegates.elena

@@ -0,0 +1,48 @@
+#import system.
+#import system'routines.
+
+#class Operable
+{
+    #method cast:verb &to:target
+        = target::verb eval &delegate:$self.
+
+    #method operate
+        = "delegate implementation".
+}
+
+#class Delegator
+{
+    #field theDelegate.
+
+    #constructor new
+    [
+        theDelegate := nil.
+    ]
+
+    #method set &Delegate:obj
+    [
+        ($nil == obj)
+            ? [ theDelegate := nil. ]
+            ! [ theDelegate := obj. ].
+    ]
+
+    #method operate
+        = theDelegate cast:%eval &to:
+            {
+                delegate : o = o operate.
+
+                ! : o = "default implementation".
+            }.
+}
+
+#symbol program =
+[
+    #var delegator := Delegator new.
+
+    ($nil, Object new, Operable new) run &each: o
+    [
+       delegator set &Delegate:o.
+
+       console writeLine:(delegator operate).
+    ].
+].

Task/Delegates/Io/delegates.io

@@ -0,0 +1,22 @@
+Delegator := Object clone do(
+    delegate ::= nil
+    operation := method(
+        if((delegate != nil) and (delegate hasSlot("thing")),
+            delegate thing,
+            "default implementation"
+        )
+    )
+)
+
+Delegate := Object clone do(
+    thing := method("delegate implementation")
+)
+
+a := clone Delegator
+a operation println
+
+a setDelegate("A delegate may be any object")
+a operation println
+
+a setDelegate(Delegate clone)
+a operation println