json data = std::string_view("hi"); doesn't work?

[lethe555]

No description provided.

[nlohmann]

std::string_view is a C++17 feature. The library supports C++11 and currently does not know what std::string_view is. This should be fixed in the future. In the meantime, you may need to pass string values as std::string to the library - they are stored internally as std::string anyway, so you would need to make a copy anyway.

[theodelrieu]

You could also provide a specialization of adl_serializer<std::string_view>.

[nlohmann]

For reference, here is a possible implementation:

#include <iostream>
#include <string_view>
#include "json.hpp"

using json = nlohmann::json;

namespace nlohmann {
    template<>
    struct adl_serializer<std::string_view> {
        static void to_json(json& j, const std::string_view& value) {
            j = std::string(value.data(), value.size());
        }
        
        static void from_json(const json& j, std::string_view& value) {
            auto ref = j.get_ref<const std::string&>();
            value = std::string_view(ref.data(), ref.size());
        }
    };
}

int main(int argc, char* argv[]) {
    json data = std::string_view("hi");
    std::cout << data << std::endl;
    data = "hello";
    std::string_view sv = data;
    std::cout << sv << std::endl;
}

[gregmarr]

Note that the lifetime of data here must be at least as long as the lifetime of sv, or you'll end up with dangling pointers in sv.

[lethe555]

I only add adl_serializer::to_json , adl_serializer::from_json may lead to a mistake with the description above
thanks!

[nlohmann]

FYI: After merging #1028, conversions from/to std::string_view are now supported out of the box.

[JasonDictos]

For the next guy:

        static void from_json(const json& j, std::string_view& value) {
            auto ref = j.get_ref<const std::string&>();
            value = std::string_view(ref.data(), ref.size());
        }

Change 'auto ref' to 'auto &ref', otherwise the string is copied then destructed when the frame leaves, resulting in an invalid string view returned.