lagoon/example/factories/tetrahedron_mijson.cpp

This example shows the usage of the JSON-parsing automatically generated polymorphic factory to create instances of the test tetrahedron class.

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/mijson_factory.hpp>
#include <iostream>
#include <stdexcept>

#include "./tetrahedron.hpp"

int main(void)
{
    try
    {
        using namespace lagoon;
        mijson_factory_builder builder;
        mijson_factory_input in;
        auto data = in.data();
        //
        auto meta_th = reflected_class<test::tetrahedron>();
        auto th_factory = meta_th->make_factory(
            builder,
            raw_ptr(&data)
        );
        //
        const char json[] =
            "["
            "   {"
            "       'base' : {"
            "           'a' : {'x': 1, 'y': 0, 'z': 0},"
            "           'b' : {'x': 0, 'y': 1, 'z': 0},"
            "           'c' : {'x': 0, 'y': 0, 'z': 0} "
            "       },"
            "       'apex' : {'x': 0, 'y': 0, 'z': 6} "
            "   },"
            "   {"
            "       'base' : {"
            "           'a' : {'x': 1, 'y': 0, 'z': 0},"
            "           'b' : {'x': 0, 'y': 2, 'z': 0},"
            "           'c' : {'w': 0} "
            "       },"
            "       'apex' : {'x': 0, 'y': 0, 'z': 6} "
            "   },"
            "   {"
            "       'base' : {"
            "           'a' : {'x': 2, 'y': 0, 'z': 0},"
            "           'b' : {'x': 0, 'y': 2, 'z': 0},"
            "           'c' : null "
            "       },"
            "       'apex' : {'x': 0, 'y': 0, 'z': 6} "
            "   },"
            "   {"
            "       'a' : {'x': 2, 'y': 0, 'z': 0},"
            "       'b' : {'x': 0, 'y': 2, 'z': 0},"
            "       'c' : { },"
            "       'd' : {'x': 0, 'y': 0, 'z': 12} "
            "   }"
            "]";
        //
        mirror::mijson_fragment<const char*> fragment(
            json,
            json + sizeof(json) - 1
        );
        auto    i = fragment.elements().begin(),
            e = fragment.elements().end();
        while(i != e)
        {
            in.set(*i);
            // use the factory to construct a tetrahedron and calculate
            // its volume and base area
            raw_ptr pt = th_factory->new_();
            test::tetrahedron& t = *raw_cast<test::tetrahedron*>(pt);
            // ... and print them out
            std::cout << "the volume is " << t.volume() << " " << std::flush;
            std::cout << "the area of the base is " << t.base.area() << std::endl;
            meta_th->delete_(pt);
            ++i;
        }
    }
    catch(std::exception const& error)
    {
        std::cerr << "Error: " << error.what() << std::endl;
    }
    //
    return 0;
}

/* Example of output:
the volume is 1 the area of the base is 0.5
the volume is 2 the area of the base is 1
the volume is 4 the area of the base is 2
the volume is 8 the area of the base is 2
*/