Dealing with trees of different node types

Question

I am having a tree data structure that can have different types of nodes deriving from one TreeBaseNode class. I have made the tree nodes of type TreeBaseNode * which gets assigned to objects of different Special nodes at run time. How can I access aNodeAttribute from the TreeBaseNode* pointer while traversing the tree on the tree is generated (if the node is of type SpecialNodeA which I can identify from NodeType)

class TreeBaseNode
{
public:
    int NodeType;   
    TypeA commonNodeAttributeA,
    TypeB commonNodeAttributeB; 
};

class SpecialNodeA : public TreeBaseNode
{
private:

    TypeD aNodeAttribute

public:
    SpecialNodeA(int type)
    {
        NodeType = type;
    }
    //Methods   
};

class SpecialNodeB : public TreeBaseNode
{

private:

    TypeE bNodeAttribute;

public:
    //Methods


};

EDIT: changed the types

If you're accessing everything through pointers-to-base-class, it implies that you don't care what type a particular object is. But from your question, it sounds like you do care. This sounds like you need to re-think your design... — Oliver Charlesworth
I understand that the design is bad. How could I modify it. I could have just one node type with all the attributes, but some of it would not be used (depending on the NodeType). That again would be bad design, right? — softwarematter
@iNoam: Without some idea of how you intend to use your data structure, it's hard to say... — Oliver Charlesworth
@Oli Depending on the NodeType I want to use the attributes to estimate something. It is done outside the class while traversing through the nodes. For instance if it is a SpecialNodeA, I would call a function with commonNodeAttributeA, commonNodeAttributeB and aNodeAttribute as parameters. — softwarematter
@iNoam: Ok. But if aNodeAttribute and bNodeAttribute are interchangeable (i.e. if @Mihran's answer will solve your problem), then you may as well replace them with a single attribute in the base class. — Oliver Charlesworth

Mihran Hovsepyan Mihran Hovsepyan · Accepted Answer · 2011-04-26T13:57:20

There is no polymorphism of data-members of clases in c++, but you can use polymorphism of function-members. So you should declare virtual int getNodeAttribute(){} in your base class. And reimplement it in two Derived classes to return attribute what you want.

Dealing with trees of different node types

3 Answers