isInstanceOf() now works with interfaces

lib/class.js

@@ -27,10 +27,9 @@ var util = require( './util' );
 /**
  * Stores class metadata internally (ensures data is encapsulated)
  *
- * The data in this object is hashed on the class object itself. Therefore, to
+ * The data in this object is hashed a class id.
- * look up an item, you would provide the class itself as the property.
  *
- * @type  {Object.<Object, { implemented: Array.<string> }>}
+ * @type  {Object.<number, { implemented: Array.<string> }>}
  */
 var class_meta = {};
 
@@ -76,7 +75,7 @@ exports.implement = function()
     }
 
     var class_new = exports.extend( dest );
-    getMeta( class_new ).implemented = implemented;
+    getMeta( class_new.__cid ).implemented = implemented;
 
     return class_new;
 };
@@ -149,8 +148,9 @@ exports.isInstanceOf = function( type, instance )
 
     // if no metadata is available, then our remaining checks cannot be
     // performed
-    if ( !( meta = getMeta( type ) ) )
+    if ( !instance.__cid || !( meta = getMeta( instance.__cid ) ) )
     {
+        console.log( instance );
         return false;
     }
 
@@ -203,6 +203,8 @@ function Class() {};
  */
 var extend = ( function( extending )
 {
+    var class_id = 0;
+
     /**
      * Mimics class inheritance
      *
@@ -274,18 +276,20 @@ var extend = ( function( extending )
         // set up the new class
         var new_class = createCtor( abstract_methods );
 
-        setupProps( new_class, abstract_methods );
         attachPropInit( prototype, properties );
 
         new_class.prototype   = prototype;
         new_class.constructor = new_class;
 
+        // important: call after setting prototype
+        setupProps( new_class, abstract_methods, ++class_id );
+
         // lock down the new class (if supported) to ensure that we can't add
         // members at runtime
         util.freeze( new_class );
 
         // create internal metadata for the new class
-        createMeta( new_class );
+        createMeta( new_class, base.prototype.__cid );
 
         // we're done with the extension process
         extending = false;
@@ -360,13 +364,15 @@ var extend = ( function( extending )
  *
  * @param  {Function}        func              function (class) to set up
  * @param  {Array.<string>}  abstract_methods  list of abstract method names
+ * @param  {number}          class_id          unique id to assign to class
  *
  * @return  {undefined}
  */
-function setupProps( func, abstract_methods )
+function setupProps( func, abstract_methods, class_id )
 {
     attachAbstract( func, abstract_methods );
     attachExtend( func );
+    attachId( func, class_id );
 }
 
 
@@ -466,6 +472,25 @@ function attachExtend( func )
 }
 
 
+/**
+ * Attaches the unique id to the class and its prototype
+ *
+ * The unique identifier is used internally to match a class and its instances
+ * with the class metadata. Exposing the id breaks encapsulation to a degree,
+ * but is a lesser evil when compared to exposing all metadata.
+ *
+ * @param  {Function}  func  function (class) to attach method to
+ * @param  {number}    id    id to assign
+ *
+ * @return  {undefined}
+ */
+function attachId( func, id )
+{
+    util.defineSecureProp( func, '__cid', id );
+    util.defineSecureProp( func.prototype, '__cid', id );
+}
+
+
 /**
  * Attaches partially applied isInstanceOf() method to class instance
  *
@@ -488,15 +513,30 @@ function attachInstanceOf( instance )
 /**
  * Initializes class metadata for the given class
  *
- * @param  {Class}  obj  class to initialize metadata for
+ * @param  {Class}  func  class to initialize metadata for
  *
  * @return  {undefined}
  */
-function createMeta( obj )
+function createMeta( func, parent_id )
 {
-    class_meta[ obj ] = {
+    var id          = func.__cid,
+        parent_meta = ( ( parent_id ) ? getMeta( parent_id) : undefined );
+
+    // copy the parent prototype's metadata if it exists (inherit metadata)
+    if ( parent_meta )
+    {
+        // todo: deep (1) util.clone() when available
+        class_meta[ id ] = {
+            implemented: util.clone( parent_meta.implemented ),
+        };
+    }
+    else
+    {
+        // create empty
+        class_meta[ id ] = {
             implemented: [],
         };
+    }
 }
 
 
@@ -506,12 +546,12 @@ function createMeta( obj )
  * Since a reference is returned (rather than a copy), the returned object can
  * be modified to alter the metadata.
  *
- * @param  {Class}  obj  class to retrieve metadata for
+ * @param  {number}  id  id of class to retrieve metadata for
  *
  * @return  {Object}
  */
-function getMeta( obj )
+function getMeta( id )
 {
-    return class_meta[ obj ];
+    return class_meta[ id ];
 }
 

test/test-class-implement.js

@@ -77,3 +77,21 @@ assert.ok(
     "Abstract methods list contains names of implemented methods"
 );
 
+
+// concrete implementation so that we can instantiate it
+var ConcreteFoo = Foo.extend(
+    {
+        foo:  function() {},
+        foo2: function() {},
+    }),
+
+    concrete_inst = new ConcreteFoo();
+
+assert.ok(
+    ( concrete_inst.isInstanceOf( Type )
+        && concrete_inst.isInstanceOf( Type2 )
+    ),
+    "Instances of classes implementing interfaces are considered to be " +
+        "instances of the implemented interfaces"
+);
+

test/test-class.js

@@ -132,3 +132,15 @@ assert.equal(
     "Class instance contains isA() alias for isInstanceOf() partially applied function"
 );
 
+
+
+assert.ok(
+    ( Foo.__cid !== undefined ),
+    "Class id available via class"
+);
+
+assert.ok(
+    ( Foo.prototype.__cid !== undefined ),
+    "Class id available via class prototype"
+);
+