Tweak in getRoleMember() method

Author: mbrowne

dci/dci-amd.js

@@ -2,21 +2,63 @@ define(["require", "exports"], function(require, exports) {
     var isNodeJs = (typeof window == 'undefined' && typeof global != 'undefined');
     var globalNamespace = isNodeJs ? global : window;
 
+    if (!isNodeJs) {
+        if (!Function.prototype.bind) {
+            Function.prototype.bind = function (oThis) {
+                if (typeof this !== "function") {
+                    throw new TypeError("Function.prototype.bind - what is trying to be bound is not callable");
+                }
+
+                var aArgs = Array.prototype.slice.call(arguments, 1), fToBind = this, fNOP = function () {
+                }, fBound = function () {
+                    return fToBind.apply(this instanceof fNOP && oThis ? this : oThis, aArgs.concat(Array.prototype.slice.call(arguments)));
+                };
+
+                fNOP.prototype = this.prototype;
+                fBound.prototype = new fNOP();
+
+                return fBound;
+            };
+        }
+    }
+
     //TODO Support DestinationAccount['de' + 'posit'](amount)
     //
     //DestinationAccount['de' + 'posit'](amount) could be rewritten to:
     //__context.__$DestinationAccount['de' + 'posit'].call(__context.DestinationAccount, amount)
     //
     //would be better to give a nice error message if role method not found:
-    //DCI.getRoleMethod(__context, 'DestinationAccount', 'de' + 'posit').call(__context.DestinationAccount, amount)
-    function getRoleMethod(context, roleName, methodName) {
-        var roleMethod = context['__$' + roleName][methodName];
-        if (!roleMethod) {
-            throw new Error('Method "' + methodName + '" not found on role "' + roleName + '"');
+    //DCI.getRoleMember(__context, __context.DestinationAccount, 'DestinationAccount', 'de' + 'posit').call(__context.DestinationAccount, amount)
+    //Gets a member on a role player - can be either a role method or a method or property of the role player object
+    function getRoleMember(context, player, roleName, memberName) {
+        if (player != context[roleName]) {
+            //If we're here, it's because the programmer used `this` inside a closure inside a role method.
+            //So either `this` refers to some other object besides the current role, or the programmer used `this`
+            //inside a closure when they should have used `self`.
+            //
+            //In other words this code would also be reached if `this` is equal to `undefined`, `global`, or `window`.)
+            //...for example, if the SourceAccount.transferOut() method in the Transfer Money example contained the following code:
+            //	[1,2,3].forEach(function() {
+            //		this.withdraw();  //`this` is actually equal to `window` or `global` here! (or `undefined` in strict mode)
+            //	});
+            //
+            //Because we need to account for the first case (`this` refers to some other object besides the current role),
+            //which is perfectly valid, we simply return the property on `this` just as would happen normally in Javascript.
+            return player[memberName];
+        }
+
+        var roleMethod = context['__$' + roleName][memberName];
+        if (roleMethod) {
+            //bind the role player as `this` on the specified role method
+            return roleMethod.bind(player);
+        } else {
+            if (!(memberName in player)) {
+                throw new Error('Method or property "' + memberName + '" not found on role "' + roleName + '" nor on its current role player.');
+            }
+            return player[memberName];
         }
-        return roleMethod;
     }
-    exports.getRoleMethod = getRoleMethod;
+    exports.getRoleMember = getRoleMember;
 
     //This function is for handling calls beginning with `this`; it calls a method on the current role player,
     //which could be either a role method or a method on the data object.

dci/dci.js

@@ -51,7 +51,7 @@ function getRoleMember(context, player, roleName, memberName) {
         //bind the role player as `this` on the specified role method
         return roleMethod.bind(player);
     } else {
-        if (!player[memberName]) {
+        if (!(memberName in player)) {
             throw new Error('Method or property "' + memberName + '" not found on role "' + roleName + '" nor on its current role player.');
         }
         return player[memberName];

dci/dci.ts

@@ -114,7 +114,7 @@ export function getRoleMember(context: Object, player: Object, roleName: string,
     }
     else {
 	    //check for property on role player
-    	if (!player[memberName]) {
+    	if (!(memberName in player)) {
     		throw new Error('Method or property "' + memberName + '" not found on role "' + roleName + '" nor on its current role player.');
     	}
     	return player[memberName];