Thanks for your explanation!
Regards,
On Fri, Apr 26, 2013 at 1:15 PM, Mateusz Loskot <[email protected]> wrote:
> On 21 April 2013 10:38, Ricardo Muñoz <[email protected]> wrote:
> > Hi, I've been trying to use boost::tuple with a boost::optional element
> and
> > I get a bad::cast exception. Attached to this mail you can find the
> complete
> > test case but here is small code snippet:
> >
> > That works:
> > row_type get_last_row(soci::session& sql)
> > {
> > unsigned int id = 0;
> > std::string str1;
> > boost::optional<std::string> str2;
> >
> > sql << "SELECT id, str1, str2 from example ORDER BY id DESC LIMIT 1",
> > soci::into(id), soci::into(str1), soci::into(str2);
>
> This is simple conversion that is performed by SQLite 3 backend itself
> which translates SQL type to C++ type as implemented in
> sqlite3_standard_into_type_backend::post_fetch
>
>
> > That does not:
> > row_type get_last_row2(soci::session& sql)
> > {
> > row_type myrow;
> >
> > try
> > {
> > sql << "SELECT id, str1, str2 from example ORDER BY id DESC LIMIT 1",
> > soci::into(myrow);
>
> Shortly, this is known issue related to this report
> https://github.com/SOCI/soci/issues/90
>
> The row_type is mapped to dynamic-typed objects wrapped with type_holder
> This is involves more complex conversion using the common layer
> of type_conversion specialisations, and here is the problem.
> If you look at type_conversion<unsigned int> in unsigned-types.h, you can
> see
> a little hack for base_type being long long.
>
> Now, at binding, statements creates type_holder<int> according to
> bind_into<dt_integer> mapping in statement_impl - there is no
> dt_unsigned_integer.
> But, the conversion goes through type_holder<long long> which leads to
> failure of dynamic_cast in type-holder.h:
>
> type_holder<T>* p = dynamic_cast<type_holder<T> *>(this);
>
> as this is type_holder<int> but T is long long, unrelated types.
>
> Long story short, this is all related to lack of complete C++ integer
> types support.
>
> Best regards,
> --
> Mateusz Loskot, http://mateusz.loskot.net
>
>
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