Listing 6: Abstract class for reading a database

// Query.h: 
#if !defined(QUERY_H)
#define QUERY_H

#include "DBXFace.h"
#include "Connect.h"

struct SortSpec
{
    int field;
    int order;
};

class Query : public DBXFace
{
public:
    BOOL execute(UINT = CRecordset::snapshot);

    // Query navigation functions
    BOOL first();
    BOOL last();
    BOOL next();
    BOOL prev();
    BOOL move(long);
    BOOL isEmpty() const;
    BOOL isEOF() const;
    BOOL isBOF() const;
    long getRecordCount() const;

    // Query-building functions
    virtual char* SQLName(int) const = 0;
    void startSelect();
    void addSelectCriteria(int,
                           const CString&);
    void addSelect();
    void endSelect();
    void resetSelect();

    void startOrder();
    void addOrderCriteria(int, int);
    void endOrder();
    void resetOrder();

    // Accessors for attributes retrieved
    // from table
    virtual long getObjID() const = 0;
    virtual CString getDesc() const = 0;

    // Accessors for this class
    CString getFilter() const;
    CString getSort() const;
    void setFilter(const CString& filt);
    void setSort(const CString& srt);

protected:
    Query(CRecordset*, Connection*);
    CString buildClause(int, const CString&);

    CString filter;
    CString sort;

private:
    enum {MAXSORTSPEC = 10};
    SortSpec sortSpecs[MAXSORTSPEC];
    int nSortSpecs;
    BOOL newClause;

    // Disallowed ops:
    Query(const Query&);
    void operator=(const Query&);
};

#endif

/* End of File */