从私有向量公开访问和分配运算符

Question

I am working in a code in C++ where a class that I created stores a vector of boost/dynamic_bitset as a private field. I need to be able to access and modify any position in the vector to do bitset operations (&, |, ^, ...).

It's possible to expose the vector assignment ( = ) and access( [] ) operators without having to reimplement them? Just like I did with iterators.

Here is the header:

class graph{
  typedef vector<boost::dynamic_bitset<>> tgraph;

  node person;
  tgraph gg;

 public:
  graph();
  graph(const uint person, const uint max_days, const uint max_nodes);

  void add_encounter_index(const node);
  void add_encounter_index(const node, const node, const node);

  void dump(ofstream& f, const vector<encounter>&);

  // iterators
  using iterator = tgraph::iterator;
  // using pointer = tgraph::value_type;
  using reference = tgraph::reference;
  // using value_type = tgraph::value_type;

  using const_iterator = tgraph::const_iterator;
  using const_reference = tgraph::const_reference;


  iterator begin() { return gg.begin(); }
  iterator end() { return gg.end(); }

  const_iterator begin() const { return gg.begin(); }
  const_iterator end() const { return gg.end(); }
  const_iterator cbegin() const { return gg.cbegin(); }
  const_iterator cend() const { return gg.cend(); }

};

Answer 1

You can overload operator[] for graph so that it resolves to a reference to the vector element, eg:

// Inline member function
auto& operator[](size_t index)
{
    return gg[i];
}

(In older versions of C++ you'll need to specify the dynamic_bitset type instead of auto ). This enables you to use:

graph1[i] = dynamic_bitset<>(size);

and other such statements. You could overload operator= , but that applies to the usage graph1 = , and it can get confusing to overload this operator to do something different to its default behaviour. So if just the operator[] overload suits your requirements then I'd recommend just doing that one.