C++: Setters and Getters for Arrays - c++

Question

I am struggling to find the correct format for initializing a (private) array within a class and getting/setting the values from outside the class.
My code is semi-functional, but feels awkward in incorrectly formatted.
It is returning only the first element of the array, I want it to return all the contents. Read code comments for additional details.
Note: This is (a very small part of) a project I am working on for school -- an array must be used, not a vector or list.
student.h
class Student {
public:
// Upon researching my issue, I read suggestions on passing pointers for arrays:
void SetDaysToCompleteCourse(int* daysToCompleteCourse[3]);
int* GetDaysToCompleteCourse(); // Ditto # above comment.
private:
int daysToCompleteCourse[3];
student.cpp
#include "student.h"
void Student::SetDaysToCompleteCourse(int* daysToCompleteCourse) {
// this->daysToCompleteCourse = daysToCompleteCourse; returns error (expression must be a modifiable lvalue)
// Feels wrong, probably is wrong:
this->daysToCompleteCourse[0] = daysToCompleteCourse[0];
this->daysToCompleteCourse[1] = daysToCompleteCourse[1];
this->daysToCompleteCourse[2] = daysToCompleteCourse[2];
}
int* Student::GetDaysToCompleteCourse() {
return daysToCompleteCourse;
}
ConsoleApplication1.cpp
#include "pch.h"
#include <iostream>
#include "student.h"
int main()
{
Student student;
int daysToCompleteCourse[3] = { 1, 2, 3 };
int* ptr = daysToCompleteCourse;
student.SetDaysToCompleteCourse(ptr);
std::cout << *student.GetDaysToCompleteCourse(); // returns first element of the array (1).
}
I gave this my best shot, but I think I need a nudge in the right direction.
Any tips here would be greatly appreciated.

Answer 1

I would say:
// student.h
class Student
{
public:
// If you can, don't use numbers:
// you have a 3 on the variable,
// a 3 on the function, etc.
// Use a #define on C or a static const on C++
static const int SIZE= 3;
// You can also use it outside the class as Student::SIZE
public:
void SetDaysToCompleteCourse(int* daysToCompleteCourse);
// The consts are for "correctness"
// const int* means "don't modify this data" (you have a setter for that)
// the second const means: this function doesn't modify the student
// whithout the const, student.GetDaysToCompleteCourse()[100]= 1 is
// "legal" C++ to the eyes of the compiler
const int* GetDaysToCompleteCourse() const; // Ditto # above comment.
Student()
{
// Always initialize variables
for (int i= 0; i < SIZE; i++) {
daysToCompleteCourse[i]= 0;
}
}
private:
int daysToCompleteCourse[SIZE];
// On GCC, you can do
//int daysToCompleteCourse[SIZE]{};
// Which will allow you not to specify it on the constructor
};
// student.cpp
void Student::SetDaysToCompleteCourse(int* newDaysToCompleteCourse)
{
// It's not wrong, just that
// this->daysToCompleteCourse[0] = daysToCompleteCourse[0];
// use another name like newDaysToCompleteCourse and then you can suppress this->
// And use a for loop
for (int i= 0; i < SIZE; i++) {
daysToCompleteCourse[i]= newDaysToCompleteCourse[i];
}
}
const int* Student::GetDaysToCompleteCourse() const
{
return daysToCompleteCourse;
}
// main.cpp
#include <iostream>
std::ostream& operator<<(std::ostream& stream, const Student& student)
{
const int* toShow= student.GetDaysToCompleteCourse();
for (int i= 0; i < Student::SIZE; i++) {
stream << toShow[i] << ' ';
}
return stream;
}
int main()
{
Student student;
int daysToCompleteCourse[3] = { 1, 2, 3 };
// You don't need this
//int* ptr = daysToCompleteCourse;
//student.SetDaysToCompleteCourse(ptr);
//You can just do:
student.SetDaysToCompleteCourse(daysToCompleteCourse);
// On C++ int* is "a pointer to an int"
// It doesn't specify how many of them
// Arrays are represented just by the pointer to the first element
// It's the FASTEST and CHEAPEST way... but you need the SIZE
const int* toShow= student.GetDaysToCompleteCourse();
for (int i= 0; i < Student::SIZE; i++) {
std::cout << toShow[i] << ' ';
// Also works:
//std::cout << student.GetDaysToCompleteCourse()[i] << ' ';
}
std::cout << std::endl;
// Or you can do: (because we defined operator<< for a ostream and a Student)
std::cout << student << std::endl;
}
You can check out it live here: https://ideone.com/DeJ2Nt