deploy: 7c9208bfb3

api/macros/json_use_implicit_conversions/index.md

@@ -0,0 +1,55 @@
+# 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.