json/docs/mkdocs/docs/api/macros/json_disable_enum_serialization.md

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: 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 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: 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 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: 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 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)
{
    if (ch == Choice::first)
    {
        j = "first";
    }
    else if (ch == Choice::second)
    {
        j = "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

• :simple-cmake: JSON_DisableEnumSerialization - CMake option to control the macro
• NLOHMANN_JSON_SERIALIZE_ENUM - serialize/deserialize an enum
• Specializing enum conversion - map enums to JSON strings instead of integers

Version history

• Added in version 3.11.0.