Question

i need to write a program in which main() would read a file(containing some predefined instructions) and create classes for each line and if a class object was already created, create a new class object.. something like

main()
{
     read file;
     save to a vector;

     for(i < vectorsize; i++)
          if(vector[i]== "book")
                 if(book b was already created) 
                       book c; 
                 else book b;
}

Answer 1

You might use a std::map to store the created books. A map is a key->value store where you can adress the content by a own defined key.

typedef std::map<std::string, Book> BookMap;
int main()
{
     read file;
     save to a vector;
     BookMap books;

     for(i < vectorsize; i++)
          if(vector[i]== "book")
                 BookMap::const_iterator alreadyCreatedBook(books.find(b.name));
                  // When there is no book in the map, the map returns it's end() element
                 if(books.end() != createdBook)
                       alreadyCreatedBook->second; 
                 else
                     books[b.name] = b;
}