d3e347bd2d
* mkdocs: add string_view examples * mkdocs: reference underlying operators * mkdocs: add operator<=> examples * mkdocs: fix style check issues * mkdocs: tweak BJData page * mkdocs: add CMake option hints to macros * mkdocs: fix JSON_DISABLE_ENUM_SERIALIZATION definition * mkdocs: fix link to unit-udt.cpp * mkdocs: fix "Arbitrary Type Conversions" title * mkdocs: link to api/macros/*.md instead of features/macros.md * mkdocs: document JSON_DisableEnumSerialization CMake option * mkdocs: encode required C++ standard in example files * docset: detect gsed/sed * docset: update index * docset: fix CSS patching * docset: add list_missing_pages make target * docset: add list_removed_paths make target * docset: replace page titles with name from index * docset: add install target for Zeal docset browser * Use GCC_TOOL in ci_test_documentation target
3.8 KiB
3.8 KiB
JSON_DISABLE_ENUM_SERIALIZATION
#define JSON_DISABLE_ENUM_SERIALIZATION /* value */
When defined to 1, default serialization and deserialization functions for enums are excluded and have to be provided
by the user, for example, using NLOHMANN_JSON_SERIALIZE_ENUM (see
arbitrary type conversions for more details).
Parsing or serializing an enum will result in a compiler error.
This works for both unscoped and scoped enums.
Default definition
The default value is 0.
#define JSON_DISABLE_ENUM_SERIALIZATION 0
Notes
!!! hint "CMake option"
Enum serialization can also be controlled with the CMake option
[`JSON_DisableEnumSerialization`](../../integration/cmake.md#json_disableenumserialization)
(`OFF` by default) which defines `JSON_DISABLE_ENUM_SERIALIZATION` accordingly.
Examples
??? example "Example 1: Disabled behavior"
The code below forces the library **not** to create default serialization/deserialization functions `from_json` and `to_json`, meaning the code below
**does not** compile.
```cpp
#define JSON_DISABLE_ENUM_SERIALIZATION 1
#include <nlohmann/json.hpp>
using json = nlohmann::json;
enum class Choice
{
first,
second,
};
int main()
{
// normally invokes to_json serialization function but with JSON_DISABLE_ENUM_SERIALIZATION defined, it does not
const json j = Choice::first;
// normally invokes from_json parse function but with JSON_DISABLE_ENUM_SERIALIZATION defined, it does not
Choice ch = j.get<Choice>();
}
```
??? example "Example 2: Serialize enum macro"
The code below forces the library **not** to create default serialization/deserialization functions `from_json` and `to_json`, but uses
[`NLOHMANN_JSON_SERIALIZE_ENUM`](nlohmann_json_serialize_enum.md) to parse and serialize the enum.
```cpp
#define JSON_DISABLE_ENUM_SERIALIZATION 1
#include <nlohmann/json.hpp>
using json = nlohmann::json;
enum class Choice
{
first,
second,
};
NLOHMANN_JSON_SERIALIZE_ENUM(Choice,
{
{ Choice::first, "first" },
{ Choice::second, "second" },
})
int main()
{
// uses user-defined to_json function defined by macro
const json j = Choice::first;
// uses user-defined from_json function defined by macro
Choice ch = j.get<Choice>();
}
```
??? example "Example 3: User-defined serialization/deserialization functions"
The code below forces the library **not** to create default serialization/deserialization functions `from_json` and `to_json`, but uses user-defined
functions to parse and serialize the enum.
```cpp
#define JSON_DISABLE_ENUM_SERIALIZATION 1
#include <nlohmann/json.hpp>
using json = nlohmann::json;
enum class Choice
{
first,
second,
};
void from_json(const json& j, Choice& ch)
{
auto value = j.get<std::string>();
if (value == "first")
{
ch = Choice::first;
}
else if (value == "second")
{
ch = Choice::second;
}
}
void to_json(json& j, const Choice& ch)
{
auto value = j.get<std::string>();
if (value == "first")
{
ch = Choice::first;
}
else if (value == "second")
{
ch = Choice::second;
}
}
int main()
{
// uses user-defined to_json function
const json j = Choice::first;
// uses user-defined from_json function
Choice ch = j.get<Choice>();
}
```
See also
Version history
- Added in version 3.11.0.