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/*
* Copyright Andrey Semashev 2007 - 2014.
* 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)
*/
#include <cassert>
#include <cstddef>
#include <string>
#include <iostream>
#include <boost/mpl/vector.hpp>
#include <boost/log/utility/type_dispatch/static_type_dispatcher.hpp>
namespace logging = boost::log;
//[ example_util_static_type_dispatcher
// Base interface for the custom opaque value
struct my_value_base
{
virtual ~my_value_base() {}
virtual bool dispatch(logging::type_dispatcher& dispatcher) const = 0;
};
// A simple attribute value
template< typename T >
struct my_value :
public my_value_base
{
T m_value;
explicit my_value(T const& value) : m_value(value) {}
// The function passes the contained type into the dispatcher
bool dispatch(logging::type_dispatcher& dispatcher) const
{
logging::type_dispatcher::callback< T > cb = dispatcher.get_callback< T >();
if (cb)
{
cb(m_value);
return true;
}
else
return false;
}
};
// Value visitor for the supported types
struct print_visitor
{
typedef void result_type;
// Implement visitation logic for all supported types
void operator() (int const& value) const
{
std::cout << "Received int value = " << value << std::endl;
}
void operator() (double const& value) const
{
std::cout << "Received double value = " << value << std::endl;
}
void operator() (std::string const& value) const
{
std::cout << "Received string value = " << value << std::endl;
}
};
// Prints the supplied value
bool print(my_value_base const& val)
{
typedef boost::mpl::vector< int, double, std::string > types;
print_visitor visitor;
logging::static_type_dispatcher< types > disp(visitor);
return val.dispatch(disp);
}
//]
int main(int, char*[])
{
// These two attributes are supported by the dispatcher
bool res = print(my_value< std::string >("Hello world!"));
assert(res);
res = print(my_value< double >(1.2));
assert(res);
// This one is not
res = print(my_value< float >(-4.3f));
assert(!res);
return 0;
}
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