polymorphism with vars?

how to do something similar to what in http://cboard.cprogramming.com/showthread.php?t=109803
"partial polymorphism"

but this time with variables and specifically with enum
I want a var to be enum and have certain values defined for a base class while other values predefined in the base class and redefined by derived classes

What is the purpose of this enum?

I don't think you can do what you want exactly - but if you describe better what you are trying to do, perhaps we can help you with a solution.

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Mats

well i have different stations with parameters that can be written or read
there is a set of parameters which is common to all stations
other parameters instead are specific for each station

i need an uint index to identify which parameter to read (or write) upon request
i need this index to be for instance of kind enum with a base set for the common indexing and a derived specific set of values for the specific indexing

Quote:

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Originally Posted by mynickmynick

well i have different stations with parameters that can be written or read
there is a set of parameters which is common to all stations
other parameters instead are specific for each station

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I am afraid that I do not quite understand what is a "station" and what is a "parameter", and how they are related. When you say that you have different stations, do you mean that you have different station objects, or that you have different station subtypes?

Quote:

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Originally Posted by mynickmynick

i need an uint index to identify which parameter to read (or write) upon request
i need this index to be for instance of kind enum with a base set for the common indexing and a derived specific set of values for the specific indexing

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Let's not go into implementation detail so soon. What is a "request"? Who will be making such a request?

Here follows what the code i am writing looks like
Station is a Vision System with one or more cameras
parameters are image processing parameters or camera parameters

Code:

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typedef class c_StationParameters
{
public:
        Type_StationArgs * Args;
        unsigned int ToBeSaved;//periodically checked. If ==1 old parameters are backupped, new parameters are saved then this bool is reset
        MUTEX  ReadImageMutex;
        //List of Station non specific parameters (they can have different values for every station but there type is the same for all)
        float MaxProcessingMsec;        float MaxProcessingMsecRI;
       
        //..other parameters to be added here
        //..
       
        //METHODS
        virtual ~c_StationParameters(){};
       
        //General methods
        int LoadStationParameters( unsigned int Backup);
        int CheckStationParameters(); //to be rewritten like Load with the non virtual interface
        int SaveStationParameters();
        int UpdateStationParametersReadImage();
       
        //Specific methods
        virtual int LoadStationSpecificParameters( FILE  *ParFile)=0;//{printf("Calling wrong method!! ######################\n");return(0);};
        virtual int CheckStationSpecificParameters()=0;
        virtual int BackupStationSpecificParameters(FILE  *ParFile, FILE  *ParFile_BP)=0;//{return(0);};
        virtual int SaveStationSpecificParameters(FILE  *ParFile)=0;//{return(0);};
        virtual int UpdateStationSpecificParametersReadImage()=0;
       
} ALIGN Type_StationParameters;



typedef class c_Station1_Parameters : public c_StationParameters
{//this part is strictly station dependent

public:       

       

       
        virtual int LoadStationSpecificParameters(  FILE  *ParFile);
        virtual int CheckStationSpecificParameters();
        virtual int BackupStationSpecificParameters(FILE  *ParFile, FILE  *ParFile_BP);
        virtual int SaveStationSpecificParameters(FILE  *ParFile);       
       
public:
        //first image processing parameters
        //0...1024
        float Img1RulerX;  float Img1RulerXRI;

       
        //second image processing parameters
        //0...1024
        float Img2RulerX;  float Img2RulerXRI;

       
        //Processing parameters
        //0...2048
        float PacketAngleTolerance; float PacketAngleToleranceRI;


} ALIGN Type_Station1_Parameters;

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RI="ReadImage"
Of each parameter is made periodically a Read Copy so that each parameter has one copy used only by the station and another copy shared between the Station thread and the socket server thread for read requests (protected by ReadImageMutex)