Thread: dynamic array of base class pointers

  1. #1
    Registered User
    Join Date
    Nov 2003

    dynamic array of base class pointers

    For a class project I am trying to make a dynamic array of pointers to the base class and program keeps crashing. I have the base class objectType, and the derived classes balloonType, enemyType, and obstacleType. I define the array of pointers and allocate memory like this.
    objectType **m_object;
    m_object = new objectType*[m_nObjects];
            //load the objects
            for (int i = 0; i < m_nObjects; i++)
                string itemType;
                inFile >> itemType;
                if (itemType == "balloon")
                    m_object[i] = new balloonType;
                if (itemType == "obstacle")
                    m_object[i] = new obstacleType;
                if (itemType == "enemy")
                    m_object[i] = new enemyType;
                inFile >> *m_object[i];
            }objectType **m_object;
    this however is not where it crashes, it crashes when the base class function GetDepth() is called. The function is a member of objectType, here is the function definition and where it crashes

     //inside objectType class
    inline int GetDepth() { return m_depth; }
    void worldManager::DepthSort()
        //bubble sort by depth - high to low
        for (int i = 0; i < (m_nObjects - 1); i++)
            for (int j = 0; j < (m_nObjects - 1 - i); j++)
                if (m_object[j]->GetDepth() < m_object[j+1]->GetDepth())  
    //******* crashes here, it says that it 
    //cannot access memory for GetDepth()
                    objectType *tempObj = m_object[j];
                    m_object[j] = m_object[j + 1];
                    m_object[j + 1] = tempObj;

  2. #2
    Registered User
    Join Date
    Oct 2001
    > inFile >> itemType;
    Are you sure itemType is filled with either balloon, obstacle, or enemy here? Because if for some reason it isn't, no memory will get allocated by the if() statements. You might print out itemType, just to be sure.

    >        }objectType **m_object;
    Is this line just a typo?

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