How can I pass std::unique_ptr into a function

Question

How can I pass a std::unique_ptr into a function? Lets say I have the following class:

class A
{
public:
    A(int val)
    {
        _val = val         


        

Answer 1

Why can I not pass a unique_ptr into a function?

You can, but not by copy - because std::unique_ptr<> is not copy-constructible.

Surely this is the primary purpose of the construct?

Among other things, std::unique_ptr<> is designed to unequivocally mark unique ownership (as opposed to std::shared_ptr<> ).

And most strangely of all, why is this an OK way of passing it?

Because in that case, there is no copy-construction.