How to get a whole row from database using SOCI?

Question

... and save it into self-defined object type? I'm using PostgreSQL. When I have everything in one file, it works. But I wanted to split this into class-files like you always do when writing in cpp. When I divided my code into *.h and *.cpp files, I'm getting errors.

Here are my files:

test.h

class MyInt
{
public:
    MyInt();
    MyInt(int i);

    void set(int i);
    int get() const;

private:
    int i_;
};

test.cpp

#include "test.h"
#include <soci.h>
#include <postgresql/soci-postgresql.h>

MyInt::MyInt()
{

}

MyInt::MyInt(int i)
{
    this->i_ = i;
}

int MyInt::get() const
{
    return this->i_;
}

void MyInt::set(int i)
{
    this->i_ - i;
}

namespace soci
{
    template <>
    struct type_conversion<MyInt>
    {
        typedef int base_type;

        static void from_base(int i,  soci::indicator ind, MyInt & mi)
        {
            if (ind ==  soci::i_null)
            {
                throw soci_error("Null value not allowed for this type");
            }

            mi.set(i);
        }

        static void to_base(const MyInt & mi, int & i,  soci::indicator & ind)
        {
            i = mi.get();
            ind = soci::i_ok;
        }
    };
}

main.cpp

#include <iostream>
#include "test.h"

int main(int argc, char **argv)
{

    MyInt i;
    sql.open(soci::postgresql, "dbname=mydb user=postgres password=postgrespass");
    sql << "SELECT count(*) FROM person;", soci::into(i);
    std::cout << "We have " << i.get() << " persons in the database.\n";
    sql.close();

    return 0;
}

I compile it like this:

g++ main_test.cpp test.h test.cpp -o App -lsoci_core -lsoci_postgresql -ldl -lpq -I /usr/local/include/soci -I /usr/include/postgresql

and got those errors:

In file included from /usr/local/include/soci/into-type.h:13:0,
                 from /usr/local/include/soci/blob-exchange.h:12,
                 from /usr/local/include/soci/soci.h:18,
                 from main_test.cpp:3:
/usr/local/include/soci/exchange-traits.h: In instantiation of â€soci::details::exchange_traits<MyInt>â€™:
/usr/local/include/soci/into.h:29:60:   instantiated from â€soci::details::into_type_ptr soci::into(T&) [with T = MyInt, soci::details::into_type_ptr = soci::details::type_ptr<soci::details::into_type_base>]â€™
main_test.cpp:29:59:   instantiated from here
/usr/local/include/soci/exchange-traits.h:35:5: error: incomplete type â€soci::details::exchange_traits<MyInt>â€™ used in nested name specifier

THE ABOVE PROBLEM IS SOLVED, TAKE A LOOK AT @JohnBandela ANSWER.

score 2 · Accepted Answer · answered Nov 29 '12 at 20:34

2

The code where you specialize type_conversion

template<>
struct type_conversion<MyInt>

Needs to be in test.h not test.cpp. The problem is if you have it in test.cpp like you do now, it is not visible in main.cpp where you are using SOCI

answered Nov 29 '12 at 20:34

John Bandela

2,416
12
19

@Brian : That's an entirely different question, and warrants a separate post. – ildjarn Nov 29 '12 at 22:02
@JohnBandela: Thank you! It worked! :) But now I have a similar problem - I extended my class to fave two private membes - how can I now get a row from database and save it into my self-defined object? Would you be so kind and help me with this issue? Please see this topic: http://stackoverflow.com/questions/13635616/how-to-get-a-whole-row-from-database-using-soci-into-user-defined-object-type if you can, thanks :) – Brian Brown Nov 29 '12 at 22:07

How to get a whole row from database using SOCI?

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