Question

I have a few classes (heat, gas, contact, pressure) inheriting from a main one (sensor).

I have a need to store them in a vector<Sensor *> (part of the specification).

At some point in time, I need to call a function that indiscriminately stores those Sensor *. (also part of the specification, not open for discussion)

Something like this:

for(size_t i = 0; i < Sensors.size(); ++i)
    Sensors[i]->storeSensor(os) //os is an ofstream kind of object, passed onwards by reference

Where and how shall storeSensor be defined?

Is there any simple way to do this or will I need to disregard the specification? Mind you, I’m a beginner!

Thanks for your time!

Answer 1

You need to make it a pure virtual function, which you then implement in each of the derived classes. The implementation can be pretty simple:

class sensor {
   ....
   virtual void storeSensor( ostream & os ) = 0;
};

class heat : public sensor {
   ....
  void storeSensor( ostream & os ) {
     os << * this;
  }

};

class light : public sensor {
   ....
  void storeSensor( ostream & os ) {
     os << * this;
  }

};

This assumes you have defined a suitable operator<< for each of your classes. If not, you need to write the specific sensors member variables explicitly. And that is the easy bit – the difficulty starts when you want to read the sensors back in again 🙂