Re: List of template classes

Quinlan Morake <>
Tue, 10 Sep 2013 14:02:38 -0700 (PDT)
On Tuesday, 10 September 2013 22:54:15 UTC+3, Leigh Johnston wrote:

On 10/09/2013 20:40, Quinlan Morake wrote:

Good day,



I have the following code and am uncertain as to how it should best don=

e / thought of. I'm creating a "data access layer", and am aware that there=
 are c++ libraries for this, but am just doing it for the practice. I would=
 like to have a dbField class, that holds the various column info, that is =
the name, type and data. A dbClass would then hold a list of dbFields, mapp=
ing to the columns available in the table. The dbField will thus have diffe=
rent data depending on that of the database column, i.e. integer / varchar =
/ bit etc.



My implementation thinking is as follows



enum eDbFieldType




   Varchar, Integer, Boolean





template <class T>


class dbField






     // Name of column in the database


     QString fieldName;


     // Column datatype


     eDbFieldType dtColumn;


     // Data the field contains


     T data;





     void setData(T);


     T getData();





class DbClass






     map<QString, dbField<> > mDbFields;





After loading the data from the database into the dbField, I may have t=

o do other things to it depending on its type, for example to base64 decode=
/encode, etc when getData() is called, and then return the data.



I figure I could use a void* for data, is that what is generally done i=

n this type of situation? I've read that templates are preferable to void* =
but is that the case here and can they be used? Or should I be thinking dif=
ferently and do something different? I'm ideally trying to avoid casting.

Take a look at boost.variant.

Thanks Leigh, will have a look. Is my thinking about it okay, as in, in thi=
s type of scenario, is that what is usually done?

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