CCArray存入对象, 用objectAtIndex取，有时取到的值为NULL

Cocos2d-x
#1

还没找到原因，用vector<Dot*>替换CCArray后没有问题，求高人解答。

在继承自CCLayer的GameLayer中，声明成员变量 :
cocos2d::CCArray* dotList;

在init()函数中创建CCArray对象，并addObject81个对象dot :
dotList = new CCArray;
dotList->initWithCapacity(DOT_ROW_AMOUNT*DOT_COL_AMOUNT);
CC_SAFE_RETAIN(dotList);

在ccTouchBegan函数内，可以取到dotList的对象，但是在connectedDots函数中取不到

DEBUG时，只看到有四个对象:

bool DotGameLayer::ccTouchBegan(cocos2d::CCTouch pTouch, cocos2d::CCEvent pEvent)
{
int selectedIndex = 5; // drowDOT_COL_AMOUNT + dcol;
Dot selectedDot = (Dot*)dotList->objectAtIndex(selectedIndex);
dotList->retain();
CCArray* dots = connectedDots(*selectedDot);
printf(“dots number:%d \n”,dots->count());

return true;

}

//四连通法取所有相连的点, dotList不为空，但取到的值为NULL
CCArray* DotGameLayer::connectedDots(Dot& aDot)
{
int visited;
CCArray* expand = new CCArray();
expand->addObject(&aDot);
int i = 0;
do
{
Dot* currentDot = (Dot*)dotList->objectAtIndex(i);

    //up dot
    int y_up = currentDot->row - 1;
    int x_up = currentDot->column;
    int index_up = y_up * DOT_COL_AMOUNT + x_up;
    if (y_up >= 0 && (visited == 0) )
    {
        Dot* cd = (Dot*)dotList->objectAtIndex(index_up);
        if (cd->type == currentDot->type)
        {
            expand->addObject(cd);
            visited = 2;
        }else
        {
            visited = 1;
        }
    }
    
    //left dot
    int y_left = currentDot->row;
    int x_left = currentDot->column - 1;
    int index_left = y_left*DOT_COL_AMOUNT + x_left;
    if (y_left >= 0 && (visited == 0) )
    {
        Dot* leftDot = (Dot*)dotList->objectAtIndex(index_left);
        if (currentDot->type == leftDot->type)
        {
            expand->addObject(leftDot);
            visited = 2;
        }else
        {
            visited = 1;
        }
    }
    
    //right dot
    int y_right = currentDot->row;
    int x_right = currentDot->column + 1;
    int index_right = y_right*DOT_COL_AMOUNT + x_right;
    if (y_right < DOT_COL_AMOUNT && (visited == 0))
    {
        Dot* rightDot = (Dot*)dotList->objectAtIndex(index_right);
        if (currentDot->type == rightDot->type)
        {
            expand->addObject(rightDot);
            visited = 2;
        }else
        {
            visited = 1;
        }
    }
    
    //down dot
    int y_down = currentDot->row + 1;
    int x_down = currentDot->column;
    int index_down = y_down*DOT_COL_AMOUNT + x_down;
    if (y_down < DOT_ROW_AMOUNT && (visited == 0))
    {
        Dot* downDot = (Dot*)dotList->objectAtIndex(index_down);
        if (currentDot->type  == downDot->type)
        {
            expand->addObject(downDot);
            visited = 2;
        }else
        {
            visited = 1;
        }
    }
    
    i++;
}while (i < expand->count());
return expand;

}