Question

I’m confused about how C++ manages objects in vector. Say I do the following:

vector<MyClass> myVector;
myVector.push_back(a);
myVector.push_back(b);
MyClass & c = myVector[1];
myVector.erase(myVector.begin());

Is the reference c still valid (or better yet, is it guaranteed to be valid)? If not, do I have to always make copy from the reference to ensure safety?

Answer 1

Is the reference c still valid (or better yet, is it guaranteed to be valid)?

Nope it is now in an undefined state.

If not, do I have to always make copy from the reference to ensure safety?

If there is a possibility of it being deleted or moved (etc) between your retrieving it and your using it, then yes you DO need to make a copy.