Classes now store implemented interfaces in a list (does not yet import methods)

lib/class.js

@@ -39,6 +39,30 @@ exports.extend = function( base )
 };
 
 
+/**
+ * Implements an interface or set of interfaces
+ *
+ * @param  {...Interface}  interfaces  interfaces to implement
+ *
+ * @return  {Class}  new class containing interface abstractions
+ */
+exports.implements = function()
+{
+    var len  = arguments.length,
+        dest = exports.extend(),
+        arg  = null;
+
+    // add each of the interfaces
+    for ( var i = 0; i < len; i++ )
+    {
+        arg = arguments[ i ];
+        dest.implemented.push( arg );
+    }
+
+    return dest;
+};
+
+
 /**
  * Determines whether the provided object is a class created through ease.js
  *
@@ -102,6 +126,19 @@ exports.isInstanceOf = function( type, instance )
     }
     catch ( e ) {}
 
+    var implemented = type.implemented;
+    if ( implemented instanceof Array )
+    {
+        var i = implemented.length;
+        while ( i-- )
+        {
+            if ( implemented[ i ] === type )
+            {
+                return true;
+            }
+        }
+    }
+
     return false;
 };
 
@@ -300,6 +337,7 @@ function setupProps( func, abstract_methods )
 {
     attachAbstract( func, abstract_methods );
     attachExtend( func );
+    attachImplemented( func );
 }
 
 
@@ -399,6 +437,19 @@ function attachExtend( func )
 }
 
 
+/**
+ * Attaches empty list that may be populated with the implemented interfaces
+ *
+ * @param  {Function}  func  function (class) to attach method to
+ *
+ * @return  {undefined}
+ */
+function attachImplemented( func )
+{
+    util.defineSecureProp( func, 'implemented', [] );
+}
+
+
 /**
  * Attaches partially applied isInstanceOf() method to class instance
  *

test/test-class-implements.js

@@ -0,0 +1,65 @@
+/**
+ * Tests class interface implements method
+ *
+ *  Copyright (C) 2010 Mike Gerwitz
+ *
+ *  This file is part of ease.js.
+ *
+ *  ease.js is free software: you can redistribute it and/or modify it under the
+ *  terms of the GNU Lesser General Public License as published by the Free
+ *  Software Foundation, either version 3 of the License, or (at your option)
+ *  any later version.
+ *
+ *  This program is distributed in the hope that it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
+ *  for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @author  Mike Gerwitz
+ * @package test
+ */
+
+var common    = require( './common' ),
+    assert    = require( 'assert' ),
+    Class     = common.require( 'class' ),
+    Interface = common.require( 'interface' );
+
+
+var Type = Interface.extend( {
+    'abstract foo': [],
+});
+
+var Type2 = Interface.extend( {
+    'abstract foo2': [],
+});
+
+
+assert.ok(
+    ( Class.implements instanceof Function ),
+    "Class provides method to implement interfaces"
+);
+
+var Foo      = {},
+    PlainFoo = Class.extend();
+
+assert.ok(
+    ( PlainFoo.implemented instanceof Array ),
+    "Class contains empty list of implemented interfaces if " +
+        "none are implemented"
+);
+
+assert.doesNotThrow( function()
+{
+    Foo = Class.implements( Type, Type2 );
+}, Error, "Class can implement interfaces" );
+
+assert.ok(
+    ( ( Foo.implemented[ 0 ] === Type )
+        && ( Foo.implemented[ 1 ] === Type2 )
+    ),
+    "Class contains list of implemented interfaces"
+);
+