Iterating through a unique_ptr of a vector of unique_ptrs

Question

If the vector isn't unique_ptrs or if I don't have a unique_ptr to the vector (and don't dereference) it works, but with both it results in a compile error. I'm not sure what's going on.

auto v = std::make_unique<std::vector<std::unique_ptr<int>>>();
for (auto item : *v)
{

}

Answer 1

You can't copy unique pointers because... well, they are unique .

You should iterate by reference:

for (auto & item : *v)
//       ^^^