Question

I’m making a little wrapper class for sqlite. To get data to/from the database I have a class called SQLiteValue. When binding data for a query SQLiteValue instances get created on the stack and passed around a few functions. A skeleton outline of the class is below.

class SQLiteValue : public SQLiteObject
{
private:            
    // stores a pointer to the data contained (could be of varying types)
    union 
    {
        int* i;
        double* d;
        std::string* s;
        std::wstring* ws;
        BYTE* b;
    } pdata;
            int type;



public:

    SQLiteValue(const char* val);
    SQLiteValue(const wchar_t* val);
    .. and so on for varying types
    virtual ~SQLiteValue();
};

The object gets created by one of several overloaded constructors. The constructors instantiate a “member” of pdata based on their type. This is the important thing for this class. Now, the problem. I have the constructors overloaded so I get clean method calls and don’t need to explicitly call SQLiteValue(xxx). As such I don’t really want to use references for functions, so I define them like.

void BindValue(const char* name, SQLiteValue value)
query->BindValue(":username", "user2"); // the "clean" method call

Declaring them like this causes a new object to be instantiated every time (or something similar?) I call a function and so the destructor frees memory allocated for pdata. This is bad.

What I’d like to know is this. Is there a better way to achieve what I’m trying to do whilst retaining my clean method calls? At the moment I have private functions which operate by reference which solves the issue, but I don’t really like this method. It would be easy for me to forget the reference and I’d end up tracking down this same issue again.

Thanks.

Answer 1

Change BindValue to take parameter by const reference.

void BindValue(const char* name, const SQLiteValue &value)