CedarHuang / Json

基于 C++11 的一个 Json 库

Json

基于 C++11 的一个 Json 库.
文档

快速开始

包含头文件

#include "json.hpp"

生成

cedar::json j;
j["integer"] = 2;
j["floating_point"] = 123.456;
j["bool"] = true;
j["string"] = "hello world";
j["null"] = cedar::json::null();
j["array"] = cedar::json::array();
j["object"] = cedar::json::object();
for (uint32_t i = 0; i < 5; ++i) {
    j["sequence"].push_back(i);
}
// for (uint32_t i = 0; i < 5; ++i) {
//     j["sequence"][i] = i;
// } // 等价
j["object2"]["key"] = "value";

2021.01.17 增加实验性生成方式:

cedar::json j = cedar::json::object{
    {"integer", 2},
    {"floating_point", 123.456},
    {"bool", true},
    {"string", "hello world"},
    {"null", cedar::json::null()},
    {"array", cedar::json::array()},
    {"object", cedar::json::object()},
    {"sequence", cedar::json::array{
            0, 1, 2, 3, 4}},
    {"object2", cedar::json::object{
            {"key", "value"}}},
};

这两种形式完全等价.

输出

std::string s = j;

或

std::cout << j << std::endl;

得

{"array":[],"bool":true,"floating_point":123.456,"integer":2,"null":null,"object":{},"object2":{"key":"value"},"sequence":[0,1,2,3,4],"string":"hello world"}

格式化后即

{
    "array":[],
    "bool":true,
    "floating_point":123.456,
    "integer":2,
    "null":null,
    "object":{},
    "object2":{
        "key":"value"
    },
    "sequence":[
        0, 1, 2, 3, 4
    ],
    "string":"hello world"
}

Ps. 输出的 Json 的 Key 按字典序排序.

解析

cedar::json j = cedar::json::parse(
    "{\"array\":[],\"bool\":true,\"floating_point\":123.456,\"integer\":2,"
    "\"null\":null,\"object\":{},\"object2\":{\"key\":\"value\"},"
    "\"sequence\":[0,1,2,3,4],\"string\":\"hello world\"}"
);

取值

std::cout << j["bool"].cast<bool>() << std::endl;
std::cout << j["integer"].cast<int>() << std::endl;
std::cout << j["floating_point"].cast<double>() << std::endl;

得

1
2
123.456

当然也可以获取值的字符串:

std::cout << j["integer"].cast() << std::endl;
// std::cout << j["integer"].cast<string>() << std::endl;

不填写模板参数即可.

修改

for (auto &i : j["sequence"]) {
    // i 的类型为 pair<const cedar::json_key, cedar::json>
    // 在 Array 状态下, first 为数组下标, second 为 value
    // 在 Object 状态下, first 为 key, second 为 value
    i.second = (i.second.cast<int>() + 1) * 2;
}
std::cout << j["sequence"] << std::endl;

得

[2,4,6,8,10]

谢谢.