Question

I basically have a

vector<Object> vec_; 

as a class member in a cpp class. At a certain class function this vector will be filled with “Objects” just like this:

vec_.push_back(Object());

At a later time I iterate through the vector elements and keep a pointer to the best element. Then the vector is cleared as shown in the following:

Object* o_ptr = &(vec_[0]);
for (unsigned int i = 1;  i < vec_.size(); i++) {
  if (o_ptr->getCost() > vec_[i].getCost()) {
  o_ptr = &(vec_[i]);
} 

vec_.clear();

Now my question is: What happens to the objects removed from the vector? Is their lifetime over as soon as the they are removed from the vector? And does the pointer also point to empty space then?
And if not when does the lifetime of these objects end?

Regards scr

Answer 1

What happens to the objects removed from the vector?

They are destructed.

Is their lifetime over as soon as the they are removed from the vector?

Yes.

Does the pointer also point to empty space then?

Yes it does. If you want to save the object, make a copy of it before clearing the vector.

It’s also important to note that certain vector operations might leave pointers pointing to nothing even if the vector is not cleared. Specifically resizes, which typically involve a reallocation. It’s generally best to store references to vector elements by index, since you will always be able to get the element via the index (whereas a pointer may be invalidated after certain operations).

The subscript operator, applied to vectors, returns a reference and does not make a copy.