Question

So I making a container class for integers and I want to overload the = operator so that I can return a deep copy of the object. My code works but the two objects point to the same address. This is the main.cpp file:

int main (int argc, const char * argv[]) {
    IntList cArray(5);

    for (int i = 0; i < cArray.getLength(); i++) {
        cArray[i] = (i + 1) * 10;
    }

    using namespace std;

    for (int i = 0; i < cArray.getLength(); i++)
        cout << cArray[i] << " ";
    cout << endl << popped << endl;

    IntList cArray2(4);

    for (int i = 0; i < cArray2.getLength(); i++)
        cArray2[i] = i * 5;

    cArray2 = cArray;
    cArray2[2] = 1000;

    for (int i = 0; i < cArray.getLength(); i++)
        cout << cArray[i] << " ";
    cout << endl;
    for (int i = 0; i < cArray2.getLength(); i++)
        cout << cArray2[i] << " ";
    cout << endl;

    return 0;
}

This is the header file for the IntList class:

class IntList {
private:
    int _length;
    int* _data;

public:
    IntList(int length);
    ~IntList();

    void erase();
    void reallocate(int length);    //  Faster way to call erase() and resize()
    void resize(int length);
    void insert(int value, int index);
    void prepend(int value);
    void append(int value);
    int pop(int index);
    void removeBefore(int index);    //  Exclusive
    void removeAfter(int index);    //  Exclusive
    int getLength();
    int indexOf(int value);

    int& operator[](int index);
    IntList operator=(IntList* source);
};

And this is the implementation of IntClass‘s operator=() method:

IntList IntList::operator=(IntList* source) {
    _length = source->getLength();

    reallocate(_length);

    for (int i = 0; i < _length; i++) {
        _data[i] = (*source)[i];
    }

    return *this;
}

Answer 1

You’re not working with pointers to IntList – operator= typically takes a const & and returns a reference to the instance being assigned to.

IntList & IntList::operator=(IntList const & source) {
  ...
  return *this;
}

Remember that you also need a copy constructor: IntList(IntList const & source)

You can make an operator= which takes a pointer to IntList – that would only work if you did something like this:

IntList l1;
IntList l2;
l1 = &l2;

This isn’t typical usage, and you should rather be explicit if you require this, use e.g. void IntList::copyFrom(IntList const *) in this case.

Other changes you should make:

Add this:

int operator[](int index) const;

Make these const:

int getLength() const;
int indexOf(int value) const;