C++ Using Setter of a member object

Question

I'm currently working on my first project using classes and objects, and I've run into a bit of a roadblock with my setter. I made up an example to illustrate the issue I'm running into (all one file for the sake of simplicity).

#include <stdio.h>
#include <iostream>
#include <string>

using namespace std;

class Example1
{
public:
    Example1() { name = "Mike"; }
    Example1(string aName) { name = aName; }
    string GetName() const { return name; }
    void SetName(string newName) { name = newName; }
private:
    string name;
};

class Example2
{
public:
    Example2() : anObj() {}
    Example2(string aName) : anObj(aName) {}
    Example1 GetObj() const { return anObj; }
    void SetObj(string objName) { anObj.SetName(objName); }
private:
    Example1 anObj;
};

int main()
{
    Example2 myObj;
    cout << myObj.GetObj().GetName() << endl;
    myObj.GetObj().SetName("Stan");
    cout << myObj.GetObj().GetName() << endl;
}

Output:

Mike 
Mike

The idea is to alter the member object in Example2 by using the member object's setter method, but the setter method doesn't seem to be working the way I expected.

I tried accessing the member by moving it to public (in Example2) and using dot notation, and that successfully changed the name. I'm not sure what the differentiation is, but, since the getter is working properly, I feel like something is wrong with how I'm using the setter.

The original problem I was trying to solve was having a Game class with a Player class member object. The idea is that the player could change their name if they wanted to.

Appreciate any help. Thanks.

Grab your C++ book of choice and read the chapter about "return by reference" / "return by value". — zett42, Nov 24 '18 at 00:11
Handy reading: [What's the difference between passing by reference vs. passing by value?](https://stackoverflow.com/questions/373419/whats-the-difference-between-passing-by-reference-vs-passing-by-value) — user4581301, Nov 24 '18 at 00:12
See how much easier your code is to read with 3 minutes of formatting? — Lightness Races in Orbit, Nov 24 '18 at 00:17
Why do you use the initialization-list for `Example2::anObj` but not for `Example1::name`? — Swordfish, Nov 24 '18 at 00:17
@LightnessRacesinOrbit No, i invest up to 5 minutes in formating ugly looking hard to read questions. But 5 is my limit. Actually, I now upvoted the q because of the short and significant code sample. — Swordfish, Nov 24 '18 at 00:19

score 3 · Accepted Answer · answered Nov 24 '18 at 00:06

All your getters return a new object. Don't. Let them return a const &. But then you need a non const getter when you modify objects to call the setters:

const Example1& GetObj() const;
Example1& GetObj();

And now, the objects that are stored underneath will be updated, and not just their copies. Same for the strings.

You can also see the fact that the setters are not working on the proper objects by using a debugger.

C++ Using Setter of a member object

Output:

1 Answers1