nlohmann json parse 基本操作示例

示例代码:

#include <iostream>
#include <unordered_map>
#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main()
{
    // create a JSON value with different types
    json json_types =
    {
        {"boolean", true},
        {
            "number", {
                {"integer", 42},
                {"floating-point", 17.23}
            }
        },
        {"string", "Hello, world!"},
        {"array", {1, 2, 3, 4, 5}},
        {"null", nullptr}
    };

    // use explicit conversions
    auto v1 = json_types["boolean"].get<bool>();
    auto v2 = json_types["number"]["integer"].get<int>();
    auto v3 = json_types["number"]["integer"].get<short>();
    auto v4 = json_types["number"]["floating-point"].get<float>();
    auto v5 = json_types["number"]["floating-point"].get<int>();
    auto v6 = json_types["string"].get<std::string>();
    auto v7 = json_types["array"].get<std::vector<short>>();
    auto v8 = json_types.get<std::unordered_map<std::string, json>>();

    // print the conversion results
    std::cout << v1 << '\n';
    std::cout << v2 << ' ' << v3 << '\n';
    std::cout << v4 << ' ' << v5 << '\n';
    std::cout << v6 << '\n';

    for (auto i : v7)
    {
        std::cout << i << ' ';
    }
    std::cout << "\n\n";

    for (auto i : v8)
    {
        std::cout << i.first << ": " << i.second << '\n';
    }
}

运行结果:

1
42 42
17.23 17
Hello, world!
1 2 3 4 5 

string: "Hello, world!"
number: {"floating-point":17.23,"integer":42}
null: null
boolean: true
array: [1,2,3,4,5]

来源信息:
https://json.nlohmann.me/api/basic_json/get/

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