c++ - Reading objects from a binary file -


i wrote program, lets enter information car, , writes object on binary file.

car car_obj; std::ofstream entr; std::ifstream ex;  void save_data() {  entr.open("main.bin", std::ios::app | std::ios::binary);      car_obj.setinfo(); entr.write((char*)&car_obj, sizeof (car_obj));  entr.close();

}

after this, have function reading binary file in order display cars have fuel consumption less user enters (the number factr in function arguments). 

void vehicles_under_factr(float factr) {  ex.open("main.bin", std::ios::app | std::ios::binary);   while (ex.read((char*)&car_obj, sizeof (car_obj)) && !ex.eof()) {      if (car_obj.fuel_cons < factr) {          car_obj.displayinfo();      } }   ex.close();

}

it works fine, if have three, or less, objects in binary file. when there more three, displays rest empty fields. if there no access after third car. why so, , can it?

i feel close solution, knowledge limited. thank in advance!

no， can't this，read（（char *）obj, sizeof(obj)）,because every object in program have memory address, allocate system. can't read address file .if object contain data, work fine, if it's element object , attribute related memory address or iterator(related memory address). work fail.


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