json/api/macros/json_has_range_view_conversion.md

JSON_HAS_RANGE_VIEW_CONVERSION

#define JSON_HAS_RANGE_VIEW_CONVERSION /* value */

This macro indicates whether a JSON array can be constructed directly from a C++20 range view (std::ranges::view), such as the result of std::views::filter or std::views::transform. Possible values are 1 when supported or 0 when unsupported.

Default definition

The default value is 1 if JSON_HAS_RANGES is 1 and the compiler is not MinGW (that is, #!cpp __MINGW32__ is not defined), and 0 otherwise.

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

!!! info "Known compiler/stdlib exclusions"

- **MinGW** -- disabled, because its `std::ranges` support is incomplete ([issue #4916](https://github.com/nlohmann/json/issues/4916)).
- All toolchains for which [`JSON_HAS_RANGES`](json_has_ranges.md#default-definition) is disabled.

Examples

??? example

The code below forces the library to disable the conversion from range views:

```cpp
#define JSON_HAS_RANGE_VIEW_CONVERSION 0
#include <nlohmann/json.hpp>

...
```

See also

• JSON_HAS_RANGES - control std::ranges support
• Constructing from a C++20 range view - usage of the feature

Version history

• Added in version 3.13.0.