jsoncpp用法

JsonCpp是一个用于处理JSON数据的C++库。以下是使用JsonCpp的一些常见用法：

1. 解析JSON字符串

#include <json/json.h>
#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    ifstream ifs("data.json");
    Json::Value root;
    Json::CharReaderBuilder readerBuilder;

    JSONCPP_STRING errs;
    if (!Json::parseFromStream(readerBuilder, ifs, &root, &errs)) {
        std::cout << errs << std::endl;
        return 1;
    }

    // use root to access json data
    std::string name = root["name"].asString();
    int age = root["age"].asInt();

    std::cout << "Name: " << name << std::endl;
    std::cout << "Age: " << age << std::endl;

    return 0;
}

2. 生成JSON字符串

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

int main()
{
    Json::Value root;
    root["name"] = "John";
    root["age"] = 30;

    Json::FastWriter writer;
    std::string json_str = writer.write(root);

    std::cout << json_str << std::endl;

    return 0;
}

3. 遍历JSON对象

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

void printJson(Json::Value &root, int depth = 0)
{
    if (root.isObject()) {
        std::cout << std::string(depth, ' ') << "{" << std::endl;
        for (auto it = root.begin(); it != root.end(); ++it) {
            std::cout << std::string(depth + 4, ' ') << it.name() << ": ";
            printJson(*it, depth + 4);
        }
        std::cout << std::string(depth, ' ') << "}" << std::endl;
    } else if (root.isArray()) {
        std::cout << std::string(depth, ' ') << "[" << std::endl;
        for (auto it = root.begin(); it != root.end(); ++it) {
            printJson(*it, depth + 4);
        }
        std::cout << std::string(depth, ' ') << "]" << std::endl;
    } else {
        std::cout << root.asString() << std::endl;
    }
}

int main()
{
    std::string json_str = "{\"name\":\"John\",\"age\":30,\"hobbies\":[\"reading\",\"swimming\"]}";

    Json::Value root;
    Json::CharReaderBuilder readerBuilder;

    JSONCPP_STRING errs;
    if (!Json::parseFromStream(readerBuilder, json_str, &root, &errs)) {
        std::cout << errs << std::endl;
        return 1;
    }

    printJson(root);

    return 0;
}

以上是JsonCpp的一些基本用法，更多用法可以参考JsonCpp的文档。