基于 C++11 的一个 Json 库.
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#include "json.hpp"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.
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.
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\"}"
);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.
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]