no container of pointers to objects in other containers

gistfile1.cpp

struct request {
  string commod;
  double pref;
}

class context {
 public:
  // adding this in the constructor will fix it until resizing occurs
  // context() {
  //   int reserve_size = 16 // a magic number
  //   requests_.reserve(reserve_size)
  // }

  void AddRequest(const request& r) {
    requests_.push_back(r); // copy r, refer only to our copy in the future
    const request& r = requests_.back();
    requests_by_commod_[r.commod].push_back(&r)
  }

 private:
  vector<request> requests_;
  map<string, vector<request*> > requests_by_commod_;
}

this fails because the address becomes invalidated when the vector resizes itself. see http://stackoverflow.com/questions/19560064/segmentation-fault-when-accessing-second-element-in-obj-vector-using-pointer