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¶
CMake option
Enum serialization can also be controlled with the CMake option JSON_DisableEnumSerialization (OFF by default) which defines JSON_DISABLE_ENUM_SERIALIZATION accordingly.
Examples¶
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.
#define JSON_DISABLE_ENUM_SERIALIZATION 1
#include<nlohmann/json.hpp>
usingjson=nlohmann::json;
enumclassChoice
{
first,
second,
};
intmain()
{
// normally invokes to_json serialization function but with JSON_DISABLE_ENUM_SERIALIZATION defined, it does not
constjsonj=Choice::first;
// normally invokes from_json parse function but with JSON_DISABLE_ENUM_SERIALIZATION defined, it does not
Choicech=j.get<Choice>();
}
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 to parse and serialize the enum.
#define JSON_DISABLE_ENUM_SERIALIZATION 1
#include<nlohmann/json.hpp>
usingjson=nlohmann::json;
enumclassChoice
{
first,
second,
};
NLOHMANN_JSON_SERIALIZE_ENUM(Choice,
{
{Choice::first,"first"},
{Choice::second,"second"},
})
intmain()
{
// uses user-defined to_json function defined by macro
constjsonj=Choice::first;
// uses user-defined from_json function defined by macro
Choicech=j.get<Choice>();
}
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.
#define JSON_DISABLE_ENUM_SERIALIZATION 1
#include<nlohmann/json.hpp>
usingjson=nlohmann::json;
enumclassChoice
{
first,
second,
};
voidfrom_json(constjson&j,Choice&ch)
{
autovalue=j.get<std::string>();
if(value=="first")
{
ch=Choice::first;
}
elseif(value=="second")
{
ch=Choice::second;
}
}
voidto_json(json&j,constChoice&ch)
{
if(ch==Choice::first)
{
j="first";
}
elseif(ch==Choice::second)
{
j="second";
}
}
intmain()
{
// uses user-defined to_json function
constjsonj=Choice::first;
// uses user-defined from_json function
Choicech=j.get<Choice>();
}
See also¶
- JSON_DisableEnumSerialization - CMake option to control the macro
NLOHMANN_JSON_SERIALIZE_ENUM- serialize/deserialize an enum
Version history¶
- Added in version 3.11.0.