issue #6: add getObjectAtIndex() to NSMutableArray

cocos2dx/cocoa/NSMutableArray.cpp

@@ -25,6 +25,7 @@ THE SOFTWARE.
 #include "NSMutableArray.h"
 #include <stdarg.h>
 #include <vector>
+#include <assert.h>
 
 using namespace std;
 
@@ -252,3 +253,16 @@ NSMutableArray* arrayWithArray(NSMutableArray *pArray)
 
 	return pNewArray;
 }
+
+NSObject* NSMutableArray::getObjectAtIndex(UINT32 uIndex)
+{
+	assert(uIndex < count());
+	assert(uIndex >= 0);
+
+	if (uIndex <= 0 || uIndex >= count())
+	{
+		return NULL;
+	}
+
+	return m_array[uIndex];
+}

cocos2dx/cocoa/NSMutableArray.h

@@ -41,6 +41,7 @@ public:
 	UINT32 getIndexOfObject(NSObject *pObject);
 	bool containsObject(NSObject *pObject);
 	NSObject* getLastObject(void);	
+	NSObject* getObjectAtIndex(UINT32 uIndex);
 
 	// Adding objects
 	void addObject(NSObject *pObject);