I have the following set up:

poster.h

template<class T>
class Poster
{
private:
    unique_ptr<Poster<T>> testPtr = nullptr;
public:
    void post(void (*callback_function)(T), T data)
    {           
        post2(testPtr, callback_function, data);
    }

    void post2(unique_ptr<Poster<T>> p, void (*callback_function)(T), T data)
    {
        callback_function(data);
    }
};
...

Then in main.cpp i have the following

void output(int x)
{
    std::cout << x;
}

int main()
{
    Poster<int> p;
    int x = 5;  
    p.post(output, x);
}

Every time i try to build this i get:

Severity    Code    Description Project File    Line    Suppression State
Error   C2280   'std::unique_ptr<Poster<int>,std::default_delete<Poster<int>>>::unique_ptr(const std::unique_ptr<Poster<int>,std::default_delete<Poster<int>>> &)': attempting to reference a deleted function  

I am not sure why this is. Any help would be greatly appreciated.

CodePudding user response：

In post2(), you take unique_ptr<Poster<T>> by value. That only works if you pass it an rvalue reference ('temporary', or something in std::move()).

From your example it's not apparent if you really need unique ownership inside post2() (not generally, but in the function). If you don't need ownership, you might take unique_ptr<Poster<T>>& p, or even simply just Poster<T>& p. If you want ownership to be transferred, and thus testPtr to be emptied, you can write in post(): post2(std::move(testPtr2), ...);