Re: Class name

From:
Barry <dhb2000@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Fri, 4 Apr 2008 19:00:32 -0700 (PDT)
Message-ID:
<bd170569-f2a6-49d1-99c3-748a39e04c38@a23g2000hsc.googlegroups.com>
On Apr 5, 9:51 am, worlman...@yahoo.com wrote:

Why the following header file - database.h must put

class Database;
class Table;

at the beginning?

Is that if I define multiple Class in a single .h file, then I need to
put all Class name at the beginning?

================
class Database;
class Table;

class Database
{
public:
        CnnPtr m_Cnn;
        char m_ErrStr[500];
        Database();
        bool Open(char* UserName, char* Pwd,char* CnnStr);
        bool Execute(char* CmdStr, Table& Tbl);


                                     ^^^^^^^^
It's because you use "Table" as reference here, then you need
"forward declaration" to let complier know this is a class name.

Maybe you can have a look at
http://www.parashift.com/c++-faq-lite/misc-technical-issues.html#faq-39.12

        void GetErrorErrStr(char* ErrStr);

};

class Table{
public:
        RecPtr m_Rec;
        char m_ErrStr[500];
        Table();
        void GetErrorErrStr(char* ErrStr);
        int ISEOF();
        HRESULT MoveNext();
        HRESULT MovePrevious();
        HRESULT MoveFirst();
        HRESULT MoveLast();

        bool Get(char* FieldName, char* FieldValue);
        bool Get(char* FieldName,SYSTEMTIME& FieldValue);
        bool Get(char* FieldName,float& FieldValue);
        bool Get(char* FieldName,double& FieldValue);
        bool Get(char* FieldName,double& FieldValue,int Scale);
        bool Get(char* FieldName,long& FieldValue);

    BOOL VariantTimeToSystemTimeWithMilliseconds (/*input*/ double
dVariantTime, /*output*/SYSTEMTIME *st);

};

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