assimp.assimp/code/Common/Maybe.h

/*
Open Asset Import Library (assimp)
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*/
#pragma once

#include <assimp/ai_assert.h>
#include <utility>

namespace Assimp {

/// @brief This class implements an optional type
/// @tparam T   The type to store.
template <typename T>
struct Maybe {
    /// @brief
    Maybe() = default;

    /// @brief
    /// @param val
    template <typename U>
    explicit Maybe(U &&val) :
            _val(std::forward<U>(val)), _valid(true) {}

    /// @brief Validate the value
    /// @return true if valid.
    operator bool() const {
        return _valid;
    }

    /// @brief Will assign a value.
    /// @param v The new valid value.
    template <typename U>
    void Set(U &&v) {
        ai_assert(!_valid);

        _valid = true;
        _val = std::forward<U>(v);
    }

    /// @brief  Will return the value when it is valid.
    /// @return The value.
    const T &Get() const {
        ai_assert(_valid);
        return _val;
    }

    Maybe &operator&() = delete;
    Maybe(const Maybe &) = delete;

private:
    T _val;
    bool _valid = false;
};

} // namespace Assimp