Question

Please assume a resource managing class, let’s say

template<typename AddressFields>
class AddressBook 
{ 
  std::list<AddressBookEntry<AddressFields> > book; 
};

which holds a list of AddressBookEntry objects. AddressBookEntry basically is supposed to consists of a couple of default member variables plus a customizable fields variable described by the templated AddressFields:

template<typename AddressFields>
struct AddressBookEntry
{
  int id;
  AddressFields fields;
};

I’d like to provide a few basic structures such as

struct Name 
{
  std::string n_first;
  std::string n_last;
};

struct Address
{
  std::string street;
  int zip;
  std::string city;
};

struct Mobile
{
  std::string m_number
};

Now my question is: Is there a way to create new structures based on the existing structures ? I want to allow a user to create his/her own custom AddressFields type by combining, for example, “Name” and “Mobile” to

struct NameMobile
{
  std::string n_first;
  std::string n_last;
  std::string m_number;
};

so it can be plugged into AddressBook. But only with already existing structures.

Answer 1

There is most certainly. It’s called multiple inheritance:

struct NameMobile : Name, Mobile {};

This aggregates Name and Mobile into a new type NameMobile (including all their members, recursively). Since you’re declaring it with the struct keyword, the public modifiers (before Name and Mobile) are implied and can thus be omitted.