single_view.h

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#pragma once
 
#include "di/container/view/view_interface.h"
#include "di/meta/language.h"
#include "di/meta/operations.h"
#include "di/types/in_place.h"
#include "di/types/size_t.h"
#include "di/util/addressof.h"
#include "di/util/forward.h"
#include "di/util/move.h"
 
namespace di::container {
template<concepts::Movable T>
requires(concepts::Object<T>)
class SingleView : public ViewInterface<SingleView<T>> {
public:
    constexpr SingleView()
    requires(concepts::DefaultInitializable<T>)
    = default;
 
    constexpr explicit SingleView(T const& value)
    requires(concepts::CopyConstructible<T>)
        : m_value(value) {}
 
    constexpr explicit SingleView(T&& value) : m_value(util::move(value)) {}
 
    template<typename... Args>
    requires(concepts::ConstructibleFrom<T, Args...>)
    constexpr explicit SingleView(types::InPlace, Args&&... args) : m_value(util::forward<Args>(args)...) {}
 
    constexpr auto begin() -> T* { return util::addressof(m_value); }
    constexpr auto begin() const -> T const* { return util::addressof(m_value); }
 
    constexpr auto end() { return begin() + 1; }
    constexpr auto end() const { return begin() + 1; }
 
    constexpr static auto size() -> types::size_t { return 1; }
 
    constexpr auto data() { return begin(); }
    constexpr auto data() const { return begin(); }
 
private:
    T m_value;
};
 
template<typename T>
SingleView(T) -> SingleView<T>;
}