# JSON_USE_IMPLICIT_CONVERSIONS

```
#define JSON_USE_IMPLICIT_CONVERSIONS /* value */
```

When defined to `0`, implicit conversions are switched off. By default, implicit conversions are switched on. The value directly affects [`operator ValueType`](https://json.nlohmann.me/api/basic_json/operator_ValueType/index.md).

## Default definition

By default, implicit conversions are enabled.

```
#define JSON_USE_IMPLICIT_CONVERSIONS 1
```

## Notes

Future behavior change

Implicit conversions will be switched off by default in the next major release of the library.

You can prepare existing code by already defining `JSON_USE_IMPLICIT_CONVERSIONS` to `0` and replace any implicit conversions with calls to [`get`](https://json.nlohmann.me/api/basic_json/get/index.md).

CMake option

Implicit conversions can also be controlled with the CMake option [`JSON_ImplicitConversions`](https://json.nlohmann.me/integration/cmake/#json_implicitconversions) (`ON` by default) which defines `JSON_USE_IMPLICIT_CONVERSIONS` accordingly.

## Examples

Example

This is an example for an implicit conversion:

```
json j = "Hello, world!";
std::string s = j;
```

When `JSON_USE_IMPLICIT_CONVERSIONS` is defined to `0`, the code above does no longer compile. Instead, it must be written like this:

```
json j = "Hello, world!";
auto s = j.get<std::string>();
```

## See also

- [**operator ValueType**](https://json.nlohmann.me/api/basic_json/operator_ValueType/index.md) - get a value (implicit)
- [**get**](https://json.nlohmann.me/api/basic_json/get/index.md) - get a value (explicit)
- [JSON_ImplicitConversions](https://json.nlohmann.me/integration/cmake/#json_implicitconversions) - CMake option to control the macro

## Version history

- Added in version 3.9.0.