Add macros NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and ..._NON_INTRUSIVE_WITH_DEFAULT (#3143)
* 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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@ -85,29 +85,31 @@ Some important things:
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If you just want to serialize/deserialize some structs, the `to_json`/`from_json` functions can be a lot of boilerplate.
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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:
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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:
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- `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(name, member1, member2, ...)` is to be defined inside the namespace of the class/struct to create code for.
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- `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.
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- `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.
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- `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.
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- `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.
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- `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.
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In both macros, the first parameter is the name of the class/struct, and all remaining parameters name the members.
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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).
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!!! note
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At most 64 member variables can be passed to `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE` or `NLOHMANN_DEFINE_TYPE_INTRUSIVE`.
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At most 64 member variables can be passed to these macros.
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??? example
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The `to_json`/`from_json` functions for the `person` struct above can be created with:
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```cpp
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namespace ns {
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NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person, name, address, age)
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}
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```
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Here is an example with private members, where `NLOHMANN_DEFINE_TYPE_INTRUSIVE` is needed:
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```cpp
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namespace ns {
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class address {
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@ -115,7 +117,7 @@ In both macros, the first parameter is the name of the class/struct, and all rem
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std::string street;
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int housenumber;
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int postcode;
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public:
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NLOHMANN_DEFINE_TYPE_INTRUSIVE(address, street, housenumber, postcode)
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};
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@ -186,12 +186,12 @@ When defined to `0`, implicit conversions are switched off. By default, implicit
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??? example
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This is an example for an implicit conversion:
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```cpp
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json j = "Hello, world!";
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std::string s = j;
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```
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When `JSON_USE_IMPLICIT_CONVERSIONS` is defined to `0`, the code above does no longer compile. Instead, it must be
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written like this:
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@ -220,6 +220,10 @@ The first parameter is the name of the class/struct, and all remaining parameter
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See [Simplify your life with macros](arbitrary_types.md#simplify-your-life-with-macros) for an example.
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## `NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(type, member...)`
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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.
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## `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(type, member...)`
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This macro can be used to simplify the serialization/deserialization of types if (1) want to use a JSON object as
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@ -231,6 +235,10 @@ first parameter is the name of the class/struct, and all remaining parameters na
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See [Simplify your life with macros](arbitrary_types.md#simplify-your-life-with-macros) for an example.
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## `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(type, member...)`
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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.
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## `NLOHMANN_JSON_SERIALIZE_ENUM(type, ...)`
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This macro simplifies the serialization/deserialization of enum types. See
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@ -334,6 +334,7 @@
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#define NLOHMANN_JSON_TO(v1) nlohmann_json_j[#v1] = nlohmann_json_t.v1;
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#define NLOHMANN_JSON_FROM(v1) nlohmann_json_j.at(#v1).get_to(nlohmann_json_t.v1);
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#define NLOHMANN_JSON_FROM_WITH_DEFAULT(v1) nlohmann_json_t.v1 = nlohmann_json_j.value(#v1, nlohmann_json_default_obj.v1);
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/*!
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@brief macro
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@ -344,6 +345,10 @@
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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__)) } \
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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__)) }
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#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Type, ...) \
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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__)) } \
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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__)) }
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/*!
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@brief macro
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@def NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE
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@ -353,6 +358,10 @@
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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__)) } \
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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__)) }
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#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(Type, ...) \
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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__)) } \
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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__)) }
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// inspired from https://stackoverflow.com/a/26745591
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// allows to call any std function as if (e.g. with begin):
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@ -2631,6 +2631,7 @@ using is_detected_convertible =
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#define NLOHMANN_JSON_TO(v1) nlohmann_json_j[#v1] = nlohmann_json_t.v1;
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#define NLOHMANN_JSON_FROM(v1) nlohmann_json_j.at(#v1).get_to(nlohmann_json_t.v1);
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#define NLOHMANN_JSON_FROM_WITH_DEFAULT(v1) nlohmann_json_t.v1 = nlohmann_json_j.value(#v1, nlohmann_json_default_obj.v1);
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/*!
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@brief macro
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@ -2641,6 +2642,10 @@ using is_detected_convertible =
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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__)) } \
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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__)) }
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#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Type, ...) \
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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__)) } \
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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__)) }
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/*!
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@brief macro
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@def NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE
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@ -2650,6 +2655,10 @@ using is_detected_convertible =
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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__)) } \
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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__)) }
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#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(Type, ...) \
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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__)) } \
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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__)) }
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// inspired from https://stackoverflow.com/a/26745591
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// allows to call any std function as if (e.g. with begin):
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@ -59,6 +59,42 @@ class person_with_private_data
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NLOHMANN_DEFINE_TYPE_INTRUSIVE(person_with_private_data, age, name, metadata)
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};
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class person_with_private_data_2
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{
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private:
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std::string name{};
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int age = 0;
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json metadata = nullptr;
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public:
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bool operator==(const person_with_private_data_2& rhs) const
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{
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return name == rhs.name && age == rhs.age && metadata == rhs.metadata;
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}
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person_with_private_data_2() = default;
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person_with_private_data_2(std::string name_, int age_, json metadata_)
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: name(std::move(name_))
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, age(age_)
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, metadata(std::move(metadata_))
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{}
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std::string getName() const
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{
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return name;
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}
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int getAge() const
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{
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return age;
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}
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json getMetadata() const
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{
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return metadata;
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}
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NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(person_with_private_data_2, age, name, metadata)
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};
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class person_without_private_data_1
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{
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public:
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@ -103,6 +139,41 @@ class person_without_private_data_2
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NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person_without_private_data_2, age, name, metadata)
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class person_without_private_data_3
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{
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public:
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std::string name{};
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int age = 0;
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json metadata = nullptr;
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bool operator==(const person_without_private_data_3& rhs) const
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{
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return name == rhs.name && age == rhs.age && metadata == rhs.metadata;
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}
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person_without_private_data_3() = default;
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person_without_private_data_3(std::string name_, int age_, json metadata_)
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: name(std::move(name_))
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, age(age_)
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, metadata(std::move(metadata_))
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{}
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std::string getName() const
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{
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return name;
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}
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int getAge() const
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{
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return age;
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}
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json getMetadata() const
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{
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return metadata;
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}
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};
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NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(person_without_private_data_3, age, name, metadata)
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class person_with_private_alphabet
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{
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public:
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@ -231,7 +302,7 @@ NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person_with_public_alphabet, a, b, c, d, e, f
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} // namespace persons
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TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRUSIVE", T,
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TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRUSIVE and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE", T,
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persons::person_with_private_data,
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persons::person_without_private_data_1,
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persons::person_without_private_data_2)
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@ -257,6 +328,40 @@ TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRU
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}
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}
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TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT", T,
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persons::person_with_private_data_2,
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persons::person_without_private_data_3)
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{
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SECTION("person with default values")
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{
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// serialization of default constructed object
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T p0;
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CHECK(json(p0).dump() == "{\"age\":0,\"metadata\":null,\"name\":\"\"}");
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// serialization
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T p1("Erik", 1, {{"haircuts", 2}});
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CHECK(json(p1).dump() == "{\"age\":1,\"metadata\":{\"haircuts\":2},\"name\":\"Erik\"}");
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// deserialization
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auto p2 = json(p1).get<T>();
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CHECK(p2 == p1);
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// roundtrip
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CHECK(T(json(p1)) == p1);
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CHECK(json(T(json(p1))) == json(p1));
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// check default value in case of missing field
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json j = json(p1);
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j.erase("name");
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j.erase("age");
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j.erase("metadata");
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T p3 = j.get<T>();
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CHECK(p3.getName() == "");
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CHECK(p3.getAge() == 0);
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CHECK(p3.getMetadata() == nullptr);
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}
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}
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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,
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persons::person_with_private_alphabet,
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persons::person_with_public_alphabet)
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