Wt

Dear Wt Team,

In DBO, how to support a table that has a binary field as primary key?

The documentation at https://www.webtoolkit.eu/wt/doc/reference/html/structWt_1_1Dbo_1_1sql_*value*_traits.html

indicates that there is a support for binary data i.e. std::vector<unsigned char>.

So if I have a DBO column of type std::vector<unsigned char>, then will I be able to set that as a primary key using Wt::Dbo::id()?

When I tried that I get an error related to stream(std::ostream) insertion operator(<<) for the binary type. As there is no default stream insertion support for std::vector<unsigned char> I implemented one:

std::ostream& operator<<(std::ostream &o, std::vector<unsigned char> const &v)
{
        for(auto i : v) {
                unsigned short d = i;
                o << std::hex << d;
        }

        return o;
}

But this does not work. I still get the following error:

wt/include/Wt/Dbo/ptr.h:372:7: error: no match for 'operator<<' (operand types are 'std::stringstream {aka std::__cxx11::basic_stringstream}' and 'Wt::Dbo::MetaDbo::IdType {aka std::vector}')

s << id();

^

This is how I implemented a table in DBO:

struct my_table
{
    std::vector<unsigned char> id;
    int dummy;

    template<typename Action>
    void persist(Action &a)
    {
        Wt::Dbo::id(a, id);
        Wt::Dbo::field(a, dummy, "dummy");
    }
};

namespace Wt {
        namespace Dbo {
                template<>
                struct dbo_traits<struct my_table> : public dbo_default_traits
                {
                                typedef std::vector<unsigned char> IdType;

                                static IdType invalidId()
                                {
                                        return std::vector<unsigned char>();
                                }

                                static const char *surrogateIdField() { return 0; }
                };
        }
};

How to support binary primary key in DBO?

Thanks and kind regards,

~Plug