Compilation error in C++ when using an assignment operator =? - c++

Question

I have written a program which was given to me as a homework assignment (it's a bit longer). The issue is that it compiles in CodeBlocks but it does not compile in Visual Studio 2017 it says - binary '=': no operator found which takes a right-hand operand of type 'CAutomobile' (or there is no acceptable conversion.
I would like to ask why is that because I could not myself find the error? I tried commenting the operator =function but still the error remained.
#include <iostream>
#include <algorithm>
#include <string>
#include <stdlib.h>
using namespace std;
class CVehicle {
string name;
int year;
public:
CVehicle() {
name = "Car";
year = 1990;
}
CVehicle(string n, int y) {
name = n;
year = y;
}
CVehicle(const CVehicle& vc) {
name = vc.name;
year = vc.year;
}
void setName(string n) {
name = n;
}
void setYear(int y) {
year = y;
}
string getName() {
return name;
}
int& getYear() {
return year;
}
virtual void Print(ostream& os) = 0;
};
class CAutomobile :public CVehicle {
double litres;
public:
CAutomobile() :CVehicle() {
litres = 7.2;
}
CAutomobile(string nm, int yr, double l) :CVehicle(nm, yr) {
litres = l;
}
void setLitres(double l) {
l = litres;
}
double& getLitres() {
return litres;
}
void Print(ostream& os) override {
os << getName() << endl;
os << getYear() << endl;
os << litres << endl;
}
friend bool operator< (CAutomobile a1, CAutomobile a2) {
if (a1.litres < a2.litres) {
return true;
}
return false;
}
CAutomobile operator= (CAutomobile& at) {
CAutomobile au;
au.getName() = at.getName();
au.getYear() = at.getYear();
au.getLitres() = at.getLitres();
return au;
}
CAutomobile operator+(CAutomobile aut) {
CAutomobile a;
a.getLitres() = getLitres() + aut.getLitres();
return a;
}
friend ostream& operator<< (ostream& o, CAutomobile a) {
o << a.getName() << endl;
o << a.getYear() << endl;
o << a.getLitres() << endl;
return o;
}
};
int main()
{
CAutomobile a[] = {
CAutomobile(),
CAutomobile("Wolkswagen",1970,80.5),
CAutomobile("Fiat",1979,21.9),
CAutomobile("Opel",1978,13.7)
};
for (int i = 0; i < sizeof(a) / sizeof(a[0]); i++) {
cout << "Name" << ' ' << a[i].getName() << endl;
cout << "Year" << ' ' << a[i].getYear() << endl;
cout << "Litres" << ' ' << a[i].getLitres() << endl;
}
int range = 2016 - 1990 + 1;
for (int i = 0; i < sizeof(a) / sizeof(a[0]); i++) {
a[i].setLitres(rand() % 100 + 1);
a[i].setYear(rand() % range + 1996);
}
//сортираме масива по литри и извеждаме
//най малкия (първия) му елемент
for (int i = 0; i < sizeof(a-1); i++) {
for (int j = 0; j < sizeof(a-1); j++) {
if (a[j].getLitres() > a[j + 1].getLitres()) {
swap(a[j], a[j + 1]);
}
}
}
cout << a[0] << endl;
CAutomobile k = a[0] + a[3];
cout << k.getLitres() << endl;
}

Answer 1

CAutomobile::operator = is completely wrong. It takes a non-const reference and assignes its field to a new object. Instead it should take a const reference and modify current object.
CAutomobile & operator =(CAutomobile const & other)
{
assert(this != ::std::addressof(other)); // check for self-assignment
SetName(other.getName());
SetYear(other.getYear());
SetLitres(other.getLitres());
return *this;
}
This will bring up another problem: getters are not const-qualified, so they should be fixes as well:
string const & getName(void) const {
return name;
}
int const & getYear(void) const {
return year;
}