json/api/macros/json_has_std_format/index.md

JSON_HAS_STD_FORMAT

#define JSON_HAS_STD_FORMAT /* value */

This macro indicates whether the standard library has support for std::format/std::formatter (that is, the <format> header). Possible values are 1 when supported or 0 when unsupported.

Default definition

The default value is detected based on the preprocessor macros JSON_HAS_CPP_20 and __cpp_lib_format.

When the macro is not defined, the library will define it to its default value.

Notes

Enabled functionality

When this macro evaluates to 1, the library provides a std::formatter<basic_json> specialization so JSON values can be used directly with std::format.

Examples

Example

The code below forces the library to disable support for std::format, even if the standard library would otherwise support it:

#define JSON_HAS_STD_FORMAT 0
#include <nlohmann/json.hpp>

...

Version history

• Added in version 3.12.x.