Differences

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--- at:tutorial:objects [2007/07/02 12:43] – jorge
+++ at:tutorial:objects [2007/07/02 13:34] – jorge
@@ Line 49: / Line 49: @@
 Every object understands the message ''new'', which creates a clone (a shallow copy) of the receiver object and initializes the clone by invoking its ''init'' method with the arguments that were passed to new (''aX'' and ''aY'' in the example of the ''point'' object). Hence, the ''init'' method plays the role of “constructor” for AmbientTalk objects. AmbientTalk’s object instantiation protocol closely corresponds to class instantiation in class-based languages, except that the new object is a clone of an existing object, rather than an empty object allocated from a class.
-AmbientTalk also provides a ''clone'' language contsruct which only creates a clone of the receiver object without calling the ''init'' method.
+AmbientTalk also provides a ''clone'' language contsruct which only creates a clone of the receiver object without calling the ''init'' method (as a matter of fact the ''new'' message desribed above does nothing more but invoking this construct and the ''init'' method subsequently).
 <code>
@@ Line 67: / Line 67: @@
 > def point3D := extend: point with: {
     def z := 0;
-    def sumofsquares() {
+    def sumOfSquares() {
-      super.sumofsquares() + z*z
+      super^sumOfSquares() + z*z
     }
   }
@@ Line 78: / Line 78: @@
 > def point3D := share: point with: {
     def z := 0;
-    def sumofsquares() {
+    def sumOfSquares() {
-      super.sumofsquares() + z*z
+      super^sumOfSquares() + z*z
     }
   }
@@ Line 88: / Line 88: @@
 <code>
-> def OpenConnection := object: {...};
+> def openConnection := object: {...};
-    def ClosedConnection := object: {...};
+  def closedConnection := object: {...};
-    def Connection := object: {
+  def connection := object: {
-      def open() {
+    def open() {
-        super := OpenConnection.new();
+      super := openConnection.new();
     };
     def close() {
-      super := ClosedConnection.new();
+      super := closedConnection.new();
     };
   }
 </code>
-===== First-class Delegation =====
+===== First-class delegation =====
+AmbientTalk provides an explicit delegation operator ''^''. The code below illustrates the use of this operator in the implementation of the ''init'' method of the ''point3D'' object.
+<code>
+> def point3D := extend: point with: {
+    def z := 0;
+    def init(aX, aY, aZ) {
+      super^init(aX, aY);
+      z := aZ;
+    };
+  }
+</code>
+A message sent to an object using this symbol (e.g. to the parent object in the example above) will first look for the method that matches the selector indicated in the message in this object (and its parents) and then execute the method body in the lexical scope of the message sender.
 ===== Encapsulation =====