mirror of
https://github.com/nlohmann/json.git
synced 2024-11-28 00:59:02 +08:00
2.5 KiB
2.5 KiB
Reference
Types and default values
JSON type | value_type | C++ type | type alias | default value |
---|---|---|---|---|
null | value_type::null |
nullptr_t |
- | nullptr |
string | value_type::string |
std::string |
JSON::string_t |
"" |
number (integer) | value_type::number |
int |
JSON::number_t |
0 |
number (floating point) | value_type::number_float |
double |
JSON::number_float_t |
0.0 |
array | value_type::array |
std::array<JSON> |
JSON::array_t |
{} |
object | value_type::object |
std::map<std::string, JSON> |
JSON::object_t |
{} |
Conversions
There are only a few type conversions possible:
- An integer number can be translated to a floating point number (e.g., by calling
get<double>()
). - A floating pointnnumber can be translated to an integer number (e.g., by calling
get<int>()
). Note the number is truncated and not rounded, ceiled or floored. - Any value but JSON objects can be translated into an array. The result is a singleton array that consists of the value before.
- Any other conversion will throw a
std::logic_error
exception.
Initialization
JSON values can be created from many literals and variable types:
JSON type | literal/variable types |
---|---|
none | nullptr literal, nullptr_t type, no value |
string | string literal, char* type, std::string type, std::string&& rvalue reference, JSON::string_t type |
number (integer) | integer literal, int type, JSON_number_t type |
number (floating point) | floating point literal, double type, JSON::number_float_t type |
array | initializer list whose elements are JSON values (or can be translated into JSON values using the rules above), std::vector<JSON> type, JSON::array_t type |
object | initializer list whose elements are pairs of a string literal and a JSON value (or can be translated into JSON values using the rules above), std::map<std::string, JSON> type, JSON::object_t type |