How to update such map structure?

I have a std::map<boost::shared_ptr<some_class>, class_descripti开发者_JAVA技巧on> class_map; where class_description is:

//Each service provides us with rules
struct class_description
{
    //A service must have
    std::string name;
            // lots of other stuff...
};

and I have another std::map<boost::shared_ptr<some_class>, class_description> class_map_new;

I need to insert pairs <boost::shared_ptr<some_class>, class_description> from class_map_new to class_map in case there was no class_description with such name in class_map before. How to do such thing?

std::map::insert doesn't allow duplicates, so you can simply attempt to insert the new values:

//Each service provides us with rules
struct class_description
{
   //A service must have
   std::string name;
   // lots of other stuff...
};

std::map<boost::shared_ptr<some_class>, class_description> class_map;
std::map<boost::shared_ptr<some_class>, class_description> class_map_new;

// insert the new values into the class_map
// using C++0x for simplicity...
for(auto new_obj = class_map_new.cbegin(), end = class_map_new.cend();
    new_obj != end; ++new_obj)
{
    auto ins_result = class_map.insert(*new_obj);

    if(false == ins_result.second)
    {
        // object was already present, 
        // ins_result.first holds the iterator
        // to the current object 
    }
    else
    {
        // object was successfully inserted
    }
}

What you want is an "stl like" algorithm for copy_if. There's not one, but you can probably find an example on the web, or write your own by looking at the code for count_if and remove_copy_if.