Re: C++ STL vectors - pointer to Vectors: do we need them?

"Daniel T." <>
Fri, 21 May 2010 16:03:39 CST
jamaj <> wrote:

I'm learning STL vectors. So, excuse me for the dummy question.

Suppose that, in some function, I create a

   vector<string> SS;

Is this vector deallocated at the end of the foo() function?


If I want to pass it to some other function that will store it
somewhere, do I need to use a vector * an allocate it someway and pass
the pointer to the vector, instead the vector itself? Does it make any
sense? If so, how do I do it?

It depends on how that function will be storing it. Some examples:

vector<string> storage;

void fn(const vector<string>& in) {
    storage = in;

int main() {
    vector<string> ss;

With the above, 'storage' and 'ss' end up with the same contents but
they are copies of each other. This is usually how it's done, especially
if "storage" is actually a member-variable of some class. (A copy is
made to support encapsulation.)

If you don't want to copy, then you need to use a pointer:

vector<string>* storage;

void fn(vector<string>* in) {
    storage = in;

int main() {
    vector<string>* v = new vector<string>;

    delete v; // you have to manually delete the vector.

Of course there are several different smart pointers that you can use to
make sure the deletion is done properly and automatically for you.

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