How to Initialize a Vector with Move-Only Types in C ?

Initialization of Vector with Move-Only Type

G attempts to copy unique_ptr objects in vector initialization, which fails due to the copy-constructor being inaccessible. The error message correctly highlights the issue of attempting to copy non-copyable objects.

Utilizing Move Iterators

To resolve this issue, you can leverage move iterators, which move elements when dereferenced:

using move_only = std::unique_ptr<int>;
move_only init[] = { move_only(), move_only(), move_only() };
std::vector<move_only> v{std::make_move_iterator(std::begin(init)),
                          std::make_move_iterator(std::end(init))};

Employing a Helper Type

Alternatively, you can utilize a helper type to achieve move semantics in initialization:

template<class T>
struct rref_wrapper
{
    explicit rref_wrapper(T&& v) : _val(std::move(v)) {}
    explicit operator T() const { return T{std::move(_val)}; }
    T&& _val;
};

// Only usable on temporaries
template<class T>
typename std::enable_if<
    !std::is_lvalue_reference<T>::value,
    rref_wrapper<T>
>::type rref(T&& v) {
    return rref_wrapper<T>(std::move(v));
}

std::initializer_list<rref_wrapper<move_only>> il{rref(move_only()),
                                                    rref(move_only()),
                                                    rref(move_only())};
std::vector<move_only> v(il.begin(), il.end());

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