Question

I want to set an element at a specific position of a vector to null, so can do it as the following:

vector<IXMLDOMNodePtr> vec1;// filled somehow
vec1[i] = nullptr;// some specific position i

ps. I want to keep the entry that is nulled, which acts like a place holder, so I think maybe vec[i] = 0 will do?

Answer 1

May be erase() will help, e.g.

vec1.erase(vec1.begin() + i);

When you iterate through next, that entry will not be there…

Now that we know what you want to do, something like this ought to work..

vector<boost::optional<IXMLDOMNodePtr> > vec1;
// populate
// to erase
vec1[i] = boost::none; // now effectively null.

This is without knowing what this IXMLDOMNodePtr is (if it is as the name implies a pointer), then simply setting it to 0 ought to work.

vec1[i] = 0;

NOTE: If you dynamically allocated this object, setting it to 0 does not clear up the memory as setting something to null does in Java – in C++ you have to explicitly clean it up first, i.e.

delete vec1[i];
vec1[i] = 0;