vectorXd from_json()？

Question

我正在尝试使用eigen::VectorXd和nlohmann-json库实现类的json序列化。将类存储为JSON字符串不是问题。如何从JSON中解析VectorXd？有没有其他的库更适合这个任务？

#include "json.hpp"

class TransformationStep {
public:
  VectorXd support_vector;
  int number;

  TransformationStep(int number_param, VectorXd support_vectorParam) {
    number = number_param;
    support_vector = support_vectorParam;
  }

  ~TransformationStep() {
  }

  //json serialization
  void to_json(nlohmann::json &j);
  void from_json(const nlohmann::json &j);
};


void TransformationStep::to_json(nlohmann::json &j) {
  j["number"] = number;
  j["support_vector"] = support_vector;
}


void Ftf::from_json(const nlohmann::json &j)
{
    number = (j.at("number").get<int>());
    //support_vector = j["support_vector"].get<VectorXd>()); //???
}

-输出调用to_json(nlohmann::json &j)

{
  "number": 3,
  "support_vector": [
    -0.00036705693279489064,
    0.020505439899631835,
    0.3531380358938106,
    0.0017673029092790872,
    -0.9333248513057808,
    0.04670404618976708,
    -0.21905858722244081,
    -1.011945322347849,
    -0.09172040021815037,
    0.008526811888809391,
    0.05187648010664058
  ]
}

Answer 1

我想出了

void vector_from_json(VectorXd& vector, const nlohmann::json &j) {
  vector.resize(j.size());
  size_t element_index=0;
  for (const auto& element : j) {
    vector(element_index++) = (double) element;
  }
}