项目地址：https://github.com/open-source-parsers/jsoncpp

函数

文件：https://github.com/open-source-parsers/jsoncpp/blob/master/include/json/value.h

String asString() const;
Int asInt() const;
  UInt asUInt() const;
#if defined(JSON_HAS_INT64)
  Int64 asInt64() const;
  UInt64 asUInt64() const;
#endif // if defined(JSON_HAS_INT64)
  LargestInt asLargestInt() const;
  LargestUInt asLargestUInt() const;
  float asFloat() const;
  double asDouble() const;
  bool asBool() const;

bool isNull() const;
  bool isBool() const;
  bool isInt() const;
  bool isInt64() const;
  bool isUInt() const;
  bool isUInt64() const;
  bool isIntegral() const;
  bool isDouble() const;
  bool isNumeric() const;
  bool isString() const;
  bool isArray() const;
  bool isObject() const;

创建 json 对象

来源：https://stackoverflow.com/questions/13293043/create-empty-json-array-with-jsoncpp

• object - Json::Value v

• array - Json::Value v = Json::Value(Json::arrayValue) 或者 jsonRootValue["emptyArray"] = Json::arrayValue;

解析字符串

#include "json/json.h"
#include <iostream>
#include <memory>

int main() {
  const std::string rawJson = R"({"Age": 20, "Name": "colin"})";
  const auto rawJsonLength = static_cast<int>(rawJson.length());
  constexpr bool shouldUseOldWay = false;
  JSONCPP_STRING err;
  Json::Value root;

  if (shouldUseOldWay) {
    Json::Reader reader;
    reader.parse(rawJson, root);
  } else {
    Json::CharReaderBuilder builder;
    const std::unique_ptr<Json::CharReader> reader(builder.newCharReader());
    if (!reader->parse(rawJson.c_str(), rawJson.c_str() + rawJsonLength, &root,
                       &err)) {
      std::cout << "error: " << err << std::endl;
      return EXIT_FAILURE;
    }
  }
  const std::string name = root["Name"].asString();
  const int age = root["Age"].asInt();

  std::cout << name << std::endl;
  std::cout << age << std::endl;
  return EXIT_SUCCESS;
}

遍历数组

for(int i = 0; i < ar.size(); i+) {
    //ar[i]
}

for(auto it = ar.begin(); it != ar.end(); it++) {
}

json序列化为字符串

#include "json/json.h"
#include <iostream>

int main() {
  Json::Value root;
  Json::Value data;
  constexpr bool shouldUseOldWay = false;
  root["action"] = "run";
  data["number"] = 1;
  root["data"] = data;

  if (shouldUseOldWay) {
    Json::FastWriter writer;
    const std::string json_file = writer.write(root);
    std::cout << json_file << std::endl;
  } else {
    Json::StreamWriterBuilder builder;
    const std::string json_file = Json::writeString(builder, root);
    std::cout << json_file << std::endl;
  }
  return EXIT_SUCCESS;
}

• isMember(“a”) 判断是否存在某个字段