Operator overloading += to add new object - c++

Question

Learning operator overloading in this project, and below in the ship.cpp file is where I think my error is.
This is the test file, I cannot change this:
#include <iostream>
#include "Ship.h"
#include "Ship.h"
#include "Engine.h"
#include "Engine.h"
using namespace std;
using namespace sdds;
void printHeader(const char* title)
{
char oldFill = cout.fill('-');
cout.width(40);
cout << "" << endl;
cout << "|> " << title << endl;
cout.fill('-');
cout.width(40);
cout << "" << endl;
cout.fill(oldFill);
}
int main()
{
{
printHeader("T1: Testing Constants");
cout << "TYPE_MAX_SIZE: " << sdds::TYPE_MAX_SIZE << endl;
cout << "MIN_STD_POWER: " << sdds::MIN_STD_POWER << endl;
cout << "MAX_STD_POWER: " << sdds::MAX_STD_POWER << endl;
cout << endl;
}
{
printHeader("T2: Testing Default Constructor");
Ship invalid;
invalid.display();
invalid += Engine("D2", 2.1);
cout << endl;
}
Engine engines[] = {
Engine("V8", 4.4),
Engine("V8", 5.0),
Engine("Inline", 4.1),
Engine("D3", 7.0),
Engine("D0", 2.0),
Engine("D1", 3.2),
};
{
printHeader("T3: Testing Custom Constructor");
Ship titanic("cruiser", engines, 6);
titanic.display();
cout << endl;
}
{
printHeader("T4: Testing Conversion to Bool Operator");
Ship invalid;
Ship titanic("liner", engines, 1);
if (invalid)
cout << "1. Test Failed! Object should be invalid.\n";
else
cout << "1. Test succeeded!\n";
if (titanic)
cout << "2. Test succeeded!\n";
else
cout << "3. Test Failed! Object should be valid.\n";
cout << endl;
}
{
printHeader("T5: Testing += and < Operators");
Ship titanic("liner", engines, 3);
char type[]{ "D0" };
while (titanic < sdds::MIN_STD_POWER)
{
type[1]++;
cout << "Ship not up to standard. Required power: "
<< sdds::MIN_STD_POWER << endl;
titanic += Engine(type, 2.1);
}
titanic.display();
if (sdds::MAX_STD_POWER < titanic)
cout << "Too much power." << endl;
else
cout << "Ship doesn't exceed power regulation of: "
<< sdds::MAX_STD_POWER << endl;
}
return 0;
}
This is my Ship.cpp file. My error is in the += operator function, where I have to add an engine but don't understand how I should approach it.
#include <iostream>
#include <cstring>
#include "Ship.h"
using namespace std;
namespace sdds {
Ship::Ship(){
m_type[0] = '\0';
m_engCnt = 0;
}
Ship::Ship(const char* type, const Engine engines[], int cnt){
if (type != nullptr && engines != nullptr && cnt > 0) {
// create a valid ship
strncpy(m_type, type, TYPE_MAX_SIZE);
for (int i = 0; i < cnt; i++) {
m_engines[i] = engines[i];
}
m_engCnt = cnt;
}else{
m_type[0] = '\0';
m_engCnt = 0;
}
}
Ship::operator bool() const {
// return true if the ship is valid (not empty)
if(m_type[0] == '\0' || m_engCnt == 0){
return false;
}else{
return true;
}
}
Ship& Ship::operator+=(Engine e){
if (!*this) {
cout << "The Object is not valid! Engine cannot be added!" << endl;
return *this;
}else if (m_engCnt == NUM_OF_ENGINES){
return *this;
}else{
// ERROR I BELIEVE IS HERE --> I dont understand the syntax to add engine here
m_engCnt++;
return *this;
}
}
double Ship::calculatePower() const {
double power = 0;
for (int i = 0; i < m_engCnt; i++) {
power += m_engines[i].get() * 5;
}
return power;
}
void Ship::display()const{
if (*this) {
cout << m_type << " - " << calculatePower() << endl;
Engine e;
for (int i = 0; i < m_engCnt; i++) {
m_engines[i].display();
}
}else{
cout << "No available data" << endl;
}
}
bool Ship::operator<(double power) const{
if (calculatePower() < power) {
return true;
}else{
return false;
}
}
bool operator<(double power, const Ship& theShip){
if (power < theShip.calculatePower()) {
return true;
}else{
return false;
}
}
}
This is my engine.cpp file:
#include <iostream>
#include <iomanip>
#include <stdio.h>
#include <string.h>
#include "Engine.h"
using namespace sdds;
using namespace std;
namespace sdds {
Engine::Engine(){
m_type[0] = '\0';
m_size = 0.0;
}
Engine::Engine(const char* type, double size){
strncpy(m_type, type, TYPE_MAX_SIZE);
m_size = size;
}
double Engine::get() const{
return m_size;
}
void Engine::display() const{
cout << m_size << " liters - " << m_type << endl;
}
}
This should be the output, but my function is stuck in the while loop:
|> T5: Testing += and < Operators
----------------------------------------
Ship not up to standard. Required power: 90.111
Ship not up to standard. Required power: 90.111
Ship not up to standard. Required power: 90.111
liner - 99
4.4 liters - V8
5 liters - V8
4.1 liters - Inline
2.1 liters - D1
2.1 liters - D2
2.1 liters - D3
Ship doesn't exceed power regulation of: 99.999

Answer 1

Your operator+= is not doing anything with the Engine that is passed to it. Your Ship class has an m_engines array, which your Ship constructor adds Engines to (without regard to NUM_OF_ENGINES, though), but your operator+= is not.
Your constructor and operator+= should look more like this instead:
Ship::Ship(const char* type, const Engine engines[], int cnt){
if (type != nullptr && engines != nullptr && cnt > 0) {
// create a valid ship
strncpy(m_type, type, TYPE_MAX_SIZE);
if (cnt > NUM_OF_ENGINES) cnt = NUM_OF_ENGINES; // <-- ADD THIS LINE!
for (int i = 0; i < cnt; ++i) {
m_engines[i] = engines[i];
}
m_engCnt = cnt;
}else{
m_type[0] = '\0';
m_engCnt = 0;
}
}
Ship& Ship::operator+=(Engine e){
if (!*this) {
cout << "The Object is not valid! Engine cannot be added!" << endl;
return *this;
}else if (m_engCnt == NUM_OF_ENGINES){
return *this;
}else{
m_engines[m_engCnt] = e; // <-- ADD THIS LINE!!!
m_engCnt++;
return *this;
}
}
I would suggest re-writing the constructor and operator+= to look more like this instead:
Ship::Ship(const char* type, const Engine engines[], int cnt){
strncpy(m_type, type != nullptr ? type : "", TYPE_MAX_SIZE);
if (engines != nullptr && cnt > 0) {
if (cnt > NUM_OF_ENGINES) cnt = NUM_OF_ENGINES;
for (int i = 0; i < cnt; ++i) {
m_engines[i] = engines[i];
}
m_engCnt = cnt;
}
else
m_engCnt = 0;
}
Ship& Ship::operator+=(const Engine &e){
if (m_type[0] != '\0' && m_engCnt < NUM_OF_ENGINES) {
m_engines[m_engCnt] = e;
++m_engCnt;
}
return *this;
}