Initialising a struct that contains a vector of itself

Question

I have a menu system that I want to initialise from constant data. A MenuItem can contain, as a sub-menu, a vector of MenuItems. But it only works

Answer 1

boost::optional and boost::recursive_wrapper look useful for this

struct S { // one brace
    boost::optional< // another brace
      boost::recursive_wrapper< // another brace
        std::vector< // another brace
          S
        >
      >
    > v; 
};

You need 4 braces for every submenu you add. Brace elision does not happen when constructor calls are involved. For example

S m{{{{ 
  {{{{ }}}}, 
  {{{{ 
    {{{{ }}}}, 
    {{{{ }}}} 
  }}}} 
}}}}; 

Honestly, using constructors look more readable

struct S {
    // this one is not really required by C++0x, but some GCC versions
    // require it.
    S(char const *s)
    :v(s) { } 

    S(std::string const& s)
    :v(s) { }

    S(std::initialize_list s)
    :v(std::vector(s)) { } 

    boost::variant<
      std::string,
      boost::recursive_wrapper<
        std::vector<
          S
        >
      >
    > v; 
};

Now it simplifies to

S s{ 
  "S1", 
  {
    "SS1",
    "SS2",
    { "SSS1", "SSS2" }
  }
};