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Add macros NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and ..._NON_INTRUSIVE_WITH_DEFAULT (#3143)

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* Added new macros NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT.

* Updated docs for NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT accordingly

* Rephrased docs for NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT

* Updated docs for NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT

* Renamed default_obj in to avoid name clashes

* Added test for serialization of default constructed object

* Add const to getters for macro tests

Co-authored-by: Chaoya Li <harry75369@gmail.com>
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pketelsen 2022-01-30 22:06:50 +01:00 committed by GitHub
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5 changed files with 145 additions and 12 deletions
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12
doc/mkdocs/docs/features/arbitrary_types.md
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@ -85,16 +85,18 @@ Some important things:
If you just want to serialize/deserialize some structs, the `to_json`/`from_json` functions can be a lot of boilerplate.
There are two macros to make your life easier as long as you (1) want to use a JSON object as serialization and (2) want to use the member variable names as object keys in that object:
There are four macros to make your life easier as long as you (1) want to use a JSON object as serialization and (2) want to use the member variable names as object keys in that object:
- `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(name, member1, member2, ...)` is to be defined inside the namespace of the class/struct to create code for.
- `NLOHMANN_DEFINE_TYPE_INTRUSIVE(name, member1, member2, ...)` is to be defined inside the class/struct to create code for. This macro can also access private members.
- `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(name, member1, member2, ...)` is to be defined inside the namespace of the class/struct to create code for. It will throw an exception in `from_json()` due to a missing value in the JSON object.
- `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(name, member1, member2, ...)` is to be defined inside the namespace of the class/struct to create code for. It will not throw an exception in `from_json()` due to a missing value in the JSON object, but fills in values from object which is default-constructed by the type.
- `NLOHMANN_DEFINE_TYPE_INTRUSIVE(name, member1, member2, ...)` is to be defined inside the class/struct to create code for. This macro can also access private members. It will throw an exception in `from_json()` due to a missing value in the JSON object.
- `NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(name, member1, member2, ...)` is to be defined inside the class/struct to create code for. This macro can also access private members. It will not throw an exception in `from_json()` due to a missing value in the JSON object, but fills in values from object which is default-constructed by the type.
In both macros, the first parameter is the name of the class/struct, and all remaining parameters name the members.
In all macros, the first parameter is the name of the class/struct, and all remaining parameters name the members. You can read more docs about them starting from [here](macros.md#nlohmann_define_type_intrusivetype-member).
!!! note
At most 64 member variables can be passed to `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE` or `NLOHMANN_DEFINE_TYPE_INTRUSIVE`.
At most 64 member variables can be passed to these macros.
??? example

8
doc/mkdocs/docs/features/macros.md
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@ -220,6 +220,10 @@ The first parameter is the name of the class/struct, and all remaining parameter
See [Simplify your life with macros](arbitrary_types.md#simplify-your-life-with-macros) for an example.
## `NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(type, member...)`
This macro is similar to `NLOHMANN_DEFINE_TYPE_INTRUSIVE`. It will not throw an exception in `from_json()` due to a missing value in the JSON object, but can throw due to a mismatched type. In order to support that it requires that the type be default constructible. The `from_json()` function default constructs an object and uses its values as the defaults when calling the `value()` function.
## `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(type, member...)`
This macro can be used to simplify the serialization/deserialization of types if (1) want to use a JSON object as
@ -231,6 +235,10 @@ first parameter is the name of the class/struct, and all remaining parameters na
See [Simplify your life with macros](arbitrary_types.md#simplify-your-life-with-macros) for an example.
## `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(type, member...)`
This macro is similar to `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE`. It will not throw an exception in `from_json()` due to a missing value in the JSON object, but can throw due to a mismatched type. In order to support that it requires that the type be default constructible. The `from_json()` function default constructs an object and uses its values as the defaults when calling the `value()` function.
## `NLOHMANN_JSON_SERIALIZE_ENUM(type, ...)`
This macro simplifies the serialization/deserialization of enum types. See

9
include/nlohmann/detail/macro_scope.hpp
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@ -334,6 +334,7 @@
#define NLOHMANN_JSON_TO(v1) nlohmann_json_j[#v1] = nlohmann_json_t.v1;
#define NLOHMANN_JSON_FROM(v1) nlohmann_json_j.at(#v1).get_to(nlohmann_json_t.v1);
#define NLOHMANN_JSON_FROM_WITH_DEFAULT(v1) nlohmann_json_t.v1 = nlohmann_json_j.value(#v1, nlohmann_json_default_obj.v1);
/*!
@brief macro
@ -344,6 +345,10 @@
friend void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
friend void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Type, ...) \
friend void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
friend void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { Type nlohmann_json_default_obj; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) }
/*!
@brief macro
@def NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE
@ -353,6 +358,10 @@
inline void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
inline void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(Type, ...) \
inline void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
inline void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { Type nlohmann_json_default_obj; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) }
// inspired from https://stackoverflow.com/a/26745591
// allows to call any std function as if (e.g. with begin):

9
single_include/nlohmann/json.hpp
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@ -2631,6 +2631,7 @@ using is_detected_convertible =
#define NLOHMANN_JSON_TO(v1) nlohmann_json_j[#v1] = nlohmann_json_t.v1;
#define NLOHMANN_JSON_FROM(v1) nlohmann_json_j.at(#v1).get_to(nlohmann_json_t.v1);
#define NLOHMANN_JSON_FROM_WITH_DEFAULT(v1) nlohmann_json_t.v1 = nlohmann_json_j.value(#v1, nlohmann_json_default_obj.v1);
/*!
@brief macro
@ -2641,6 +2642,10 @@ using is_detected_convertible =
friend void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
friend void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Type, ...) \
friend void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
friend void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { Type nlohmann_json_default_obj; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) }
/*!
@brief macro
@def NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE
@ -2650,6 +2655,10 @@ using is_detected_convertible =
inline void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
inline void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(Type, ...) \
inline void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
inline void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { Type nlohmann_json_default_obj; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) }
// inspired from https://stackoverflow.com/a/26745591
// allows to call any std function as if (e.g. with begin):

107
test/src/unit-udt_macro.cpp
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@ -59,6 +59,42 @@ class person_with_private_data
NLOHMANN_DEFINE_TYPE_INTRUSIVE(person_with_private_data, age, name, metadata)
};
class person_with_private_data_2
{
private:
std::string name{};
int age = 0;
json metadata = nullptr;
public:
bool operator==(const person_with_private_data_2& rhs) const
{
return name == rhs.name && age == rhs.age && metadata == rhs.metadata;
}
person_with_private_data_2() = default;
person_with_private_data_2(std::string name_, int age_, json metadata_)
: name(std::move(name_))
, age(age_)
, metadata(std::move(metadata_))
{}
std::string getName() const
{
return name;
}
int getAge() const
{
return age;
}
json getMetadata() const
{
return metadata;
}
NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(person_with_private_data_2, age, name, metadata)
};
class person_without_private_data_1
{
public:
@ -103,6 +139,41 @@ class person_without_private_data_2
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person_without_private_data_2, age, name, metadata)
class person_without_private_data_3
{
public:
std::string name{};
int age = 0;
json metadata = nullptr;
bool operator==(const person_without_private_data_3& rhs) const
{
return name == rhs.name && age == rhs.age && metadata == rhs.metadata;
}
person_without_private_data_3() = default;
person_without_private_data_3(std::string name_, int age_, json metadata_)
: name(std::move(name_))
, age(age_)
, metadata(std::move(metadata_))
{}
std::string getName() const
{
return name;
}
int getAge() const
{
return age;
}
json getMetadata() const
{
return metadata;
}
};
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(person_without_private_data_3, age, name, metadata)
class person_with_private_alphabet
{
public:
@ -231,7 +302,7 @@ NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person_with_public_alphabet, a, b, c, d, e, f
} // namespace persons
TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRUSIVE", T,
TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRUSIVE and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE", T,
persons::person_with_private_data,
persons::person_without_private_data_1,
persons::person_without_private_data_2)
@ -257,6 +328,40 @@ TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRU
}
}
TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT", T,
persons::person_with_private_data_2,
persons::person_without_private_data_3)
{
SECTION("person with default values")
{
// serialization of default constructed object
T p0;
CHECK(json(p0).dump() == "{\"age\":0,\"metadata\":null,\"name\":\"\"}");
// serialization
T p1("Erik", 1, {{"haircuts", 2}});
CHECK(json(p1).dump() == "{\"age\":1,\"metadata\":{\"haircuts\":2},\"name\":\"Erik\"}");
// deserialization
auto p2 = json(p1).get<T>();
CHECK(p2 == p1);
// roundtrip
CHECK(T(json(p1)) == p1);
CHECK(json(T(json(p1))) == json(p1));
// check default value in case of missing field
json j = json(p1);
j.erase("name");
j.erase("age");
j.erase("metadata");
T p3 = j.get<T>();
CHECK(p3.getName() == "");
CHECK(p3.getAge() == 0);
CHECK(p3.getMetadata() == nullptr);
}
}
TEST_CASE_TEMPLATE("Serialization/deserialization of classes with 26 public/private member variables via NLOHMANN_DEFINE_TYPE_INTRUSIVE and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE", T,
persons::person_with_private_alphabet,
persons::person_with_public_alphabet)