Question

I’m starting with C++ and I have a doubts:

I’m making a function which will return a vector of objects of a class MyClass.

vector<MyClass>* myMethod()

The first question is, it’s correct to return a pointer?

The second question is: if I’m going to return a pointer, should I also insert pointer of MyClass object into the vector?

MyClass* object;
myVector.push_back(*object);

Answer 1

There is nothing wrong with method that returns pointer to vector like this: vector<MyClass>* myMethod(). But you should ask yourself some questions, like:

1. Does it have to be pointer to vector? Can’t it be just vector<MyClass> ?
2. Should this method also allocate memory for this vector?
3. Should caller of this method delete / free this memory ?

And to your second question: I would make vector of pointers to objects of MyClass (vector<MyClass*>) only if it is really necessary. It will cause you some troubles with memory management, so let’s choose an easier way.

Ok, let’s talk about this question: Should this method also allocate memory for this vector?
If the purpose of this method is to create a vector, then yes, the method should also allocate memory for it:

vector<MyClass>* myMethod()
{
    vector<MyClass>* v = new vector<MyClass>;
    // initialize, fill or do whatever with this vector
    return v;
}

caller should clean up then:

    vector<MyClass>* v = myMethod();
    // do some stuff
    delete v; // clean up

If the purpose is just to retrieve the pointer to some specific vector that can not be obtained by caller, it could look like this:

vector<MyClass> _x; // caller can not access _x but myMethod can

vector<MyClass>* myMethod()
{
    return &_x;
}

caller shouldn’t delete this vector in this case:

    vector<MyClass>* v = myMethod();
    // do some stuff, don't delete v