Question

I was wondering:

With a tree, the root can have multiple children and no id. All nodes (except the root) have an id and the leaf nodes can not have children. It is fixed what type must be used for each depth. So the leaves are always of the same type and so are the parents of the leaves.

Since the root and the nodes can have children and only the nodes have an id I was wondering if the following use of multiple inheritance is acceptable:

class NodeWithId
{
    private:
        std::string m_id;
};

template<typename T>
class NodeWithChildren
{
    private:
        std::vector<T> m_nodes;
};

class Network: public NodeWithChildren<Subnet>
{
};

class Subnet: public NodeWithChildren<Machine>, 
                     public NodeWithId
{
};

class Machine: public NodeWithChildren<Application>, 
               public NodeWithId
{
};

class Application: public NodeWithId
{
};

Or is there a better way to implement this?

edit:

• removed virtual
• changed classnames

Answer 1

Or is there a better way to implement this?

IMHO, your design creates classes for stuff that are best treated as object instances. At a class level I do not see the need to differentiate between Level1 nodes and Level2 nodes.

Use a design that is simple. Ask yourself, if this design has any potential benefits or not than the naive approach of having a single Node class and creating a tree structure out of Node instances (which you create at runtime).