Passing an Array of Objects into a Function - c++

Question

I have a class that defines object.name as "Ben" and object.favNum as 25.
I also have an array (names) to store 5 objects of this class.
Before I output the attributes of the objects in the array, I change the value of names[0].name to "Jim" and names[0].favNum to 40, using pointer notation.
Here is my code:
#include<iostream>
class Person {
public:
std::string name = "Ben";
int favNum = 25;
};
int main()
{
Person names[5];
Person *ptr = &names[0];
// Changing Values
(ptr + 0)->name = "Jim";
(ptr + 0)->favNum = 40;
for (int i = 0; i < 5; i++)
{
std::cout << (std::string) (ptr + i)->name << std::endl;
std::cout << (int) (ptr + i)->favNum << std::endl << std::endl;
}
system("pause>0");
}
Output:
Jim
40
Ben
25
Ben
25
Ben
25
Ben
25
Where I have the "Changing Values" comment, I want to replace those 2 lines with a function.
The function will be able to change the values as I am doing with the 2 lines.
This is where I am having a problem.
I'm struggling with figuring out what type to declare the function as, how to pass the pointer in, how to receive the pointer, and how to change the values of the objects in the array in the function.

Answer 1

I would recommend against the use of pointers, unless you really need pointers.
// use references instead
void change(Person &person) {
person.name = "Jim";
person.favNum = 40;
};
int main()
{
Person names[5];
change(names[0]);
// ...
}
The appropriate way to write such a function would be using references. A reference is similar to a pointer, but can never be nullptr. In your case you don't need nullability, you just need to edit a Person without copying it.
You probably want change() to be parametric though:
// use references instead
void change(Person &person, std::string name, int favNum) {
person.name = std::move(name);
person.favNum = favNum;
}
But now you are assigning all members of Person using this function, which makes it pointless. It would be simpler if you assigned Person. Why not use a struct and aggregate initialization:
struct Person {
std::string name = "Ben";
int favNum = 25;
};
int main()
{
Person names[5];
names[0] = {"Jim", 40};
// ...
}
On a side note, what you are doing here is unnecessary complicated:
(ptr + 0)->name = "Jim";
// this is equivalent to
ptr[0].name = "Jim";
// this is equivalent to
ptr->name = "Jim";

Answer 2

This is how your code should look in "real" c++ (the setting of the values will be done in the constructor function or using the setNameAndFavNum() function):
#include <array>
#include <iostream>
struct Person {
public:
Person(const std::string& name_ = "Ben", int favNum_ = 25) : name(name_), favNum(favNum_) {};
void setNameAndFavNum(const std::string& name_, int favNum_) {
name = name_;
favNum = favNum_;
};
std::string name;
int favNum;
};
int main() {
std::array<Person, 5> names;
// Changing Values
names[0].setNameAndFavNum("Jim", 40);
// Alternatively you can use the constructor and implicit copy constructor
// names[0] = {"Jim", 40};
for (int i = 0; i < names.size(); i++) {
std::cout << names[i].name << std::endl;
std::cout << names[i].favNum << std::endl << std::endl;
}
}
You shouldn't mess around with pointers and raw values when writing c++ code.