lagoon/example/factories/person_pq.cpp

This example shows the usage of the LIBPQ based automatically generated polymorphic factory to create instances of the test person class.

This example requires access to a local postgresql database named 'test' with a table named 'person' with (more or less) the following definition (containing some data):

  CREATE TABLE person (
    first_name TEXT NOT NULL,
    middle_name TEXT.
    family_name TEXT NOT NULL,
    birth_date DATE,
    weight FLOAT,
    height FLOAT
  );

Copyright 2008-2010 Matus Chochlik. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

//
// We want to use Lagoon's polymorphic factories
#define LAGOON_MT_WITH_MAKE_FACTORY 1
//
// We don't need to traverse through namespace members.
// Using this CT switch can greatly improve compile times
// and the resulting executable size if namespace member
// traversal is not needed
#define LAGOON_NO_NAMESPACE_MEMBERS 1

#include <mirror/mirror.hpp>
#include <mirror/stream.hpp>
#include <lagoon/lagoon.hpp>
#include <lagoon/utils/libpq_factory.hpp>
#include <iostream>
#include <stdexcept>

#include "./person.hpp"
int main(void)
{
    try
    {
        using namespace lagoon;
        // connect to the database
        libpq_fact_db test_db("dbname=test");
        // query data about persons
        libpq_fact_result persons=test_db.query("SELECT * FROM person");
        // make a person object factory
        libpq_factory_builder builder;
        libpq_fact_data data(persons.data());
        auto meta_person = reflected_class<test::person>();
        auto person_factory = meta_person->make_factory(
            builder,
            raw_ptr(&data)
        );
        // go through the rows of the data-set
        while(!persons.empty())
        {
            raw_ptr ppers = person_factory->new_();
            test::person& pers = *raw_cast<test::person*>(ppers);
            std::cout <<
                // make a person from the data
                // and write it to std output
                mirror::stream::to_json::from(
                    pers,
                    [&persons](std::ostream& out)
                    {out << "person_" << persons.position();}
                ) << std::endl;
            meta_person->delete_(ppers);
            persons.next();
        }
    }
    catch(std::exception const& error)
    {
        std::cerr << "Error: " << error.what() << std::endl;
    }
    //
    return 0;
}

/* Example of output:
 |  "person_0": {
 |      "first_name": "Johnny",
 |      "middle_name": "B",
 |      "family_name": "Goode",
 |      "birth_date": {
 |          "tm_sec": 0,
 |          "tm_min": 0,
 |          "tm_hour": 0,
 |          "tm_mday": 1,
 |          "tm_mon": 0,
 |          "tm_year": 10,
 |          "tm_wday": 6,
 |          "tm_yday": 0,
 |          "tm_isdst": 0
 |      },
 |      "weight": 80.1,
 |      "height": 180
 |  }
 */