模板类的继承

Question

为什么要这样做

    class DataRefsTree;

    class DataRefsTreeComparator {
    public:
        inline bool operator()(const DataRefsTree* inFirst, const DataRefsTree* inSecond) const;
    };

    class DataRefsTree : public DataTree<AbstractDataRef*, DataRefsTree, STreeHolderSet<DataRefsTree, DataRefsTreeComparator>> {
    public:

这不起作用

template <typename Data> class BaseTree;
    class BaseTreeComparartor {
    public:
        template <typename Data> inline bool operator()(const BaseTree<Data>* inFirst, const BaseTree<Data>* inSecond) const;
    };
    template <typename Data> class BaseTree :public DataTree<Data, BaseTree<Data>, STreeHolderSet<BaseTree<Data>, BaseTreeComparator>>;
    class DataRefsTree;
    class DataRefsTree :public BaseTree<AbstractDataRef> {

错误类sasl :: AbstractDataRef的类型不完整。 如何解决？