JsonOptional.hpp

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#pragma once
 
#include <nlohmann/json.hpp>
#include <optional>
#include <string_view>
 
namespace ppforest2::serialization {
  inline bool has_value(nlohmann::json const& j, std::string_view key) {
    auto it = j.find(key);
    return it != j.end() && !it->is_null();
  }
}
 
namespace nlohmann {
  template<typename T> struct adl_serializer<std::optional<T>> {
    static void to_json(json& j, std::optional<T> const& opt) {
      if (opt) {
        j = *opt;
      } else {
        j = nullptr;
      }
    }
 
    static void from_json(json const& j, std::optional<T>& opt) {
      if (j.is_null()) {
        opt = std::nullopt;
      } else {
        opt = j.get<T>();
      }
    }
  };
}