Friend function is unable to construct a unique pointer of the class

Question

I have a certain design strategy where the constructor of my class is private and can only be constructed by friends of the class. Inside the friend function, I am trying to cre

Answer 1

Why am I not able to compile?

You are unable to compile because make_unique is not a friend of Spam.

An alternative solution to making make_unique a friend is to move the creation of the unique_ptr into Spam.

class Spam {
   ...
private:
   Spam(int) {}

   static unique_ptr create( int i ) 
   { return std::unique_ptr( new Spam(i) ); }
};

and then have Foo call that instead.

void Foo() {
    std::unique_ptr spam = Spam::create(10);
    ...
}