cpp的boost库怎么判断json值的类型

Boost库中有一个Json库，可以通过以下方式判断Json值的类型：

1. 使用value()方法获取Json值的类型枚举值，然后根据枚举值判断类型。

#include <boost/json.hpp>
using namespace boost::json;

value jv = parse(R"({ "name":"John", "age":30, "city":"New York" })");
switch (jv.kind()) {
    case kind::object:
        std::cout << "object\n";
        break;
    case kind::array:
        std::cout << "array\n";
        break;
    case kind::string:
        std::cout << "string\n";
        break;
    case kind::int64:
        std::cout << "integer\n";
        break;
    case kind::uint64:
        std::cout << "unsigned integer\n";
        break;
    case kind::double_:
        std::cout << "floating point number\n";
        break;
    case kind::bool_:
        std::cout << "boolean value\n";
        break;
    case kind::null:
        std::cout << "null value\n";
        break;
}

2. 使用is_xxx()方法判断Json值的类型。

#include <boost/json.hpp>
using namespace boost::json;

value jv = parse(R"({ "name":"John", "age":30, "city":"New York" })");
if (jv.is_object()) {
    std::cout << "object\n";
} else if (jv.is_array()) {
    std::cout << "array\n";
} else if (jv.is_string()) {
    std::cout << "string\n";
} else if (jv.is_int64()) {
    std::cout << "integer\n";
} else if (jv.is_uint64()) {
    std::cout << "unsigned integer\n";
} else if (jv.is_double()) {
    std::cout << "floating point number\n";
} else if (jv.is_bool()) {
    std::cout << "boolean value\n";
} else if (jv.is_null()) {
    std::cout << "null value\n";
}

以上两种方法都可以判断Json值的类型，根据实际情况选择使用。