Vector key gets lost when searching through it - c++

Question

I have an vector array in my class which is made to hold pointers to a specific object pointers.
The class should contain methods allowing for adding, removing and finding the objects inside.
The class right now looks like this:
class VectorKontener: public Kontener <VectorKontener> {
protected:
int find(Obiekt &n) {
cout << endl << "---------------------" << endl << "Running find method loop!" << endl;
for (int i = 0; i < stos.size(); i++) {
cout << "Now running for id: " << stos[i]->getId() << endl;
if (stos[i] == &n) return i;
}
return -1;
}
public:
VectorKontener::VectorKontener(Obiekt &n) {
add(n);
}
VectorKontener add(Obiekt &n) {
cout << "Adding: " << n.getId() << endl;
stos.push_back(&n);
return *this;
}
int checkPresent(Obiekt &n) {
return this->find(n) != -1;
}
VectorKontener remove(Obiekt &n) {
if (this->checkPresent(n)) {
stos.erase(stos.begin() + this->find(n));
}
else
cout << endl <<"ELEMENT NOT IN CONTAINER" << endl;
return *this;
}
VectorKontener display() {
cout << endl << "===DISPLAY===" << endl;
for (int i = 0; i < stos.size(); i++) {
stos[i]->display();
}
return *this;
}
};
However when running for test data of:
void Zad3()
{
Obiekt
obj1(5),
obj2(23),
obj3(234),
obj4(33);
cout << endl << "1. Class init" << endl;
VectorKontener k1(obj1);
cout << endl << "2. Adding other objects into array" << endl;
k1
.add(obj2)
.add(obj3)
.display();
cout << endl << "3. Element remove attempt" << endl;
k1
.remove(obj2)
.display();
getchar();
}
The output looks like so:
1. Class init
Adding: 5
2. Adding other objects into array
Adding: 23
Adding: 234
===DISPLAY===
This object has id: 5
This object has id: 23
This object has id: 234
3. Element remove attempt
---------------------
Running find method loop!
Now running for id: 5
Now running for id: 23
---------------------
Running find method loop!
Now running for id: 5
Now running for id: 23
===DISPLAY===
This object has id: 5
The output makes it seem like the third variable of the array becomes lost in the find method (hehe) since it is not calculated by it, despite stos.size() showing the proper value (2).
I am not a cpp expert, to be fair pretty far from it, and am aware this might be a pretty noobish issue, but I have really ran out of ways to make it work properly.
Any help would be really amazing

Answer 1

The issue is that the functions return copies of the object, meaning that in the chained add call the original object is not modified (on the second and any subsequent function call), instead a temporary one is created on each function call that gets destroyed right after.
The simple fix is to change the return value to a reference, e.g.: for the add function:
VectorKontener& add(Obiekt &n) {
instead of
VectorKontener add(Obiekt &n) {
And similar changes for the other functions.