C++ template: access members from source template struct

I want to create following class template:

Holds a list of objects of different classes derived from same base class.
This objects are all of the same size (derevied clases are same size).
Being abled to do some computation on all members from a function.
Has a member to access each object of the list individually.
List and members can be created at compilation, no need for dinamic lists.
User interface must be simple, since it will be used many times and by different programmers on the teams, with little c++ experience.
Use C++14 standard, gcc compiler.

Example of user code. This is what I want to keep as simple as possible:

//list of sensors with a member for each sensor
typedef struct {
    cOneSensor_f A4_temp1 = cOneSensor_f ("A4t1", 0x1234 /*, x, y, ... and some more configuration data*/);
    cOneSensor_i B4_speed = cOneSensor_i ("B4s0", 0x2001 /*, x, y, ... and some more configuration data*/);
}Sensor_list_4_s;

//put the list inside a class template to be able to control all of them as a whole,
//but also access each sensor individually
cSensorsList<Sensor_list_4_s> Sensor_list_4( 4 );

//get sensor values
void do_sensors_stuff()
{
    //all sensors as a whole
    Sensor_list_4.update();

    //access each sensor individually
    float A4t1 = Sensor_list_4.A4_temp1();
    int   B4s0 = Sensor_list_4.B4_speed();
}

Behind the scene It can be as complicated as needed. It could be somehting like this:

A base class for objects
Some derived classes for different objects variations (I can manage all derived classes from base)
Template class to hold the list of objects.

class cOneSensor {}
class cOneSensor_f: class cOneSensor {}
class cOneSensor_i: class cOneSensor {}

template <typename T>
class cSensorsList: public T
{
private:
    int bus_code;
    cOneSensor *p_to_sensors_array;
    int nSensors;

public:
    cSensorsList(int bus_code):bus_code(bus_code)
    {
        //---  here is what I don't know how to do: get sensor list from typename T
        nSensors = 0; //getSensorListSize_from_T(/* T */);
        p_to_sensors_array= 0;//getSensorListPointer_from_T<T>(/* T */);
        // ---
    }
    void update(void) {
        for (int i=0; i<nSensors; i++)
            p_to_sensors_array[i].update();
    }
};

With this code I get:

✅ Members on cSensorsList to access each object individually.
✅ Symple to user perspective.
✅ All objects in a class.

But I don't know how to:

❌ Within the class cSensorsList, get the list of members of template struct, to loop through all objects in the list to so some actions: pointer_to_sensors_array = getSensorListPointer_from_T().

Solution

Since base class is an struct, not a class, the this pointer points to first inherited member from template. There is not vtable.

Also, given all derived cOneSensor_X classes are the same size, we can calculate the number of members on base template struct T.

template <typename T>
class cSensorsList: public T
{
//...
public:
    cSensorsList(int bus_code):bus_code(bus_code)
    {
        nSensors = sizeof(T)/sizeof(cOneSensor);
        p_sensors_array = (cOneSensor*)this; // <<--- pointer to first inherited member
    }
    void update(void) {/*...*/}
};

Note: If derived cOneSensor_X classes are not the same size, you can try a more sophisticated algoritm and sequencially capturing initial position of each member.

But I'm pretty sure (or I wish) there should be a more elegant solution.