Merge pull request #2225 from nlohmann/issue2175
Simplify conversion from/to custom types
This commit is contained in:
Niels Lohmann
GitHub
commit
eb7376bb13
5 changed files with 245 additions and 0 deletions
36
README.md
36
README.md
|
|
@ -869,6 +869,42 @@ Some important things:
|
|||
* In function `from_json`, use function [`at()`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a93403e803947b86f4da2d1fb3345cf2c.html#a93403e803947b86f4da2d1fb3345cf2c) to access the object values rather than `operator[]`. In case a key does not exist, `at` throws an exception that you can handle, whereas `operator[]` exhibits undefined behavior.
|
||||
* You do not need to add serializers or deserializers for STL types like `std::vector`: the library already implements these.
|
||||
|
||||
#### Simplify your life with macros
|
||||
|
||||
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:
|
||||
|
||||
- `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(name, member1, member2, ...)` is to be defined inside of the namespace of the class/struct to create code for.
|
||||
- `NLOHMANN_DEFINE_TYPE_INTRUSIVE(name, member1, member2, ...)` is to be defined inside of the class/struct to create code for. This macro can also access private members.
|
||||
|
||||
In both macros, the first parameter is the name of the class/struct, and all remaining parameters name the members.
|
||||
|
||||
##### Examples
|
||||
|
||||
The `to_json`/`from_json` functions for the `person` struct above can be created with:
|
||||
|
||||
```cpp
|
||||
namespace ns {
|
||||
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person, name, address, age);
|
||||
}
|
||||
```
|
||||
|
||||
Here is an example with private members, where `NLOHMANN_DEFINE_TYPE_INTRUSIVE` is needed:
|
||||
|
||||
```cpp
|
||||
namespace ns {
|
||||
class address {
|
||||
private:
|
||||
std::string street;
|
||||
int housenumber;
|
||||
int postcode;
|
||||
|
||||
public:
|
||||
NLOHMANN_DEFINE_TYPE_INTRUSIVE(address, street, housenumber, postcode);
|
||||
};
|
||||
}
|
||||
```
|
||||
|
||||
#### How do I convert third-party types?
|
||||
|
||||
|
|
|
|||
|
|
@ -124,3 +124,44 @@
|
|||
basic_json<ObjectType, ArrayType, StringType, BooleanType, \
|
||||
NumberIntegerType, NumberUnsignedType, NumberFloatType, \
|
||||
AllocatorType, JSONSerializer, BinaryType>
|
||||
|
||||
// Macros to simplify conversion from/to types
|
||||
|
||||
#define NLOHMANN_JSON_EXPAND( x ) x
|
||||
#define NLOHMANN_JSON_GET_MACRO(_1,_2,_3,_4,_5,_6, _7, _8, _9, _10, _11, NAME,...) NAME
|
||||
|
||||
#define NLOHMANN_JSON_PASTE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_GET_MACRO(__VA_ARGS__, NLOHMANN_JSON_PASTE11, \
|
||||
NLOHMANN_JSON_PASTE10, NLOHMANN_JSON_PASTE9, NLOHMANN_JSON_PASTE8, NLOHMANN_JSON_PASTE7, \
|
||||
NLOHMANN_JSON_PASTE6, NLOHMANN_JSON_PASTE5, NLOHMANN_JSON_PASTE4, NLOHMANN_JSON_PASTE3, \
|
||||
NLOHMANN_JSON_PASTE2, NLOHMANN_JSON_PASTE1)(__VA_ARGS__))
|
||||
#define NLOHMANN_JSON_PASTE2(func, v1) func(v1)
|
||||
#define NLOHMANN_JSON_PASTE3(func, v1, v2) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE2(func, v2)
|
||||
#define NLOHMANN_JSON_PASTE4(func, v1, v2, v3) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE3(func, v2, v3)
|
||||
#define NLOHMANN_JSON_PASTE5(func, v1, v2, v3, v4) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE4(func, v2, v3, v4)
|
||||
#define NLOHMANN_JSON_PASTE6(func, v1, v2, v3, v4, v5) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE5(func, v2, v3, v4, v5)
|
||||
#define NLOHMANN_JSON_PASTE7(func, v1, v2, v3, v4, v5, v6) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE6(func, v2, v3, v4, v5, v6)
|
||||
#define NLOHMANN_JSON_PASTE8(func, v1, v2, v3, v4, v5, v6, v7) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE7(func, v2, v3, v4, v5, v6, v7)
|
||||
#define NLOHMANN_JSON_PASTE9(func, v1, v2, v3, v4, v5, v6, v7, v8) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE8(func, v2, v3, v4, v5, v6, v7, v8)
|
||||
#define NLOHMANN_JSON_PASTE10(func, v1, v2, v3, v4, v5, v6, v7, v8, v9) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE8(func, v2, v3, v4, v5, v6, v7, v8, v9)
|
||||
#define NLOHMANN_JSON_PASTE11(func, v1, v2, v3, v4, v5, v6, v7, v8, v9, v10) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE8(func, v2, v3, v4, v5, v6, v7, v8, v9, v10)
|
||||
|
||||
#define NLOHMANN_JSON_TO(v1) j[#v1] = t.v1;
|
||||
#define NLOHMANN_JSON_FROM(v1) j.at(#v1).get_to(t.v1);
|
||||
|
||||
/*!
|
||||
@brief macro
|
||||
@def NLOHMANN_DEFINE_TYPE_INTRUSIVE
|
||||
@since version 3.9.0
|
||||
*/
|
||||
#define NLOHMANN_DEFINE_TYPE_INTRUSIVE(Type, ...) \
|
||||
friend void to_json(nlohmann::json& j, const Type& t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
|
||||
friend void from_json(const nlohmann::json& j, Type& t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
|
||||
|
||||
/*!
|
||||
@brief macro
|
||||
@def NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE
|
||||
@since version 3.9.0
|
||||
*/
|
||||
#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(Type, ...) \
|
||||
void to_json(nlohmann::json& j, const Type& t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
|
||||
void from_json(const nlohmann::json& j, Type& t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
|
||||
|
|
|
|||
|
|
@ -2153,6 +2153,47 @@ JSON_HEDLEY_DIAGNOSTIC_POP
|
|||
NumberIntegerType, NumberUnsignedType, NumberFloatType, \
|
||||
AllocatorType, JSONSerializer, BinaryType>
|
||||
|
||||
// Macros to simplify conversion from/to types
|
||||
|
||||
#define NLOHMANN_JSON_EXPAND( x ) x
|
||||
#define NLOHMANN_JSON_GET_MACRO(_1,_2,_3,_4,_5,_6, _7, _8, _9, _10, _11, NAME,...) NAME
|
||||
|
||||
#define NLOHMANN_JSON_PASTE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_GET_MACRO(__VA_ARGS__, NLOHMANN_JSON_PASTE11, \
|
||||
NLOHMANN_JSON_PASTE10, NLOHMANN_JSON_PASTE9, NLOHMANN_JSON_PASTE8, NLOHMANN_JSON_PASTE7, \
|
||||
NLOHMANN_JSON_PASTE6, NLOHMANN_JSON_PASTE5, NLOHMANN_JSON_PASTE4, NLOHMANN_JSON_PASTE3, \
|
||||
NLOHMANN_JSON_PASTE2, NLOHMANN_JSON_PASTE1)(__VA_ARGS__))
|
||||
#define NLOHMANN_JSON_PASTE2(func, v1) func(v1)
|
||||
#define NLOHMANN_JSON_PASTE3(func, v1, v2) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE2(func, v2)
|
||||
#define NLOHMANN_JSON_PASTE4(func, v1, v2, v3) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE3(func, v2, v3)
|
||||
#define NLOHMANN_JSON_PASTE5(func, v1, v2, v3, v4) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE4(func, v2, v3, v4)
|
||||
#define NLOHMANN_JSON_PASTE6(func, v1, v2, v3, v4, v5) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE5(func, v2, v3, v4, v5)
|
||||
#define NLOHMANN_JSON_PASTE7(func, v1, v2, v3, v4, v5, v6) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE6(func, v2, v3, v4, v5, v6)
|
||||
#define NLOHMANN_JSON_PASTE8(func, v1, v2, v3, v4, v5, v6, v7) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE7(func, v2, v3, v4, v5, v6, v7)
|
||||
#define NLOHMANN_JSON_PASTE9(func, v1, v2, v3, v4, v5, v6, v7, v8) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE8(func, v2, v3, v4, v5, v6, v7, v8)
|
||||
#define NLOHMANN_JSON_PASTE10(func, v1, v2, v3, v4, v5, v6, v7, v8, v9) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE8(func, v2, v3, v4, v5, v6, v7, v8, v9)
|
||||
#define NLOHMANN_JSON_PASTE11(func, v1, v2, v3, v4, v5, v6, v7, v8, v9, v10) NLOHMANN_JSON_PASTE2(func, v1) NLOHMANN_JSON_PASTE8(func, v2, v3, v4, v5, v6, v7, v8, v9, v10)
|
||||
|
||||
#define NLOHMANN_JSON_TO(v1) j[#v1] = t.v1;
|
||||
#define NLOHMANN_JSON_FROM(v1) j.at(#v1).get_to(t.v1);
|
||||
|
||||
/*!
|
||||
@brief macro
|
||||
@def NLOHMANN_DEFINE_TYPE_INTRUSIVE
|
||||
@since version 3.9.0
|
||||
*/
|
||||
#define NLOHMANN_DEFINE_TYPE_INTRUSIVE(Type, ...) \
|
||||
friend void to_json(nlohmann::json& j, const Type& t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
|
||||
friend void from_json(const nlohmann::json& j, Type& t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
|
||||
|
||||
/*!
|
||||
@brief macro
|
||||
@def NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE
|
||||
@since version 3.9.0
|
||||
*/
|
||||
#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(Type, ...) \
|
||||
void to_json(nlohmann::json& j, const Type& t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
|
||||
void from_json(const nlohmann::json& j, Type& t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
|
||||
|
||||
|
||||
namespace nlohmann
|
||||
{
|
||||
|
|
|
|||
|
|
@ -132,6 +132,7 @@ set(files
|
|||
src/unit-to_chars.cpp
|
||||
src/unit-ubjson.cpp
|
||||
src/unit-udt.cpp
|
||||
src/unit-udt_macro.cpp
|
||||
src/unit-unicode.cpp
|
||||
src/unit-user_defined_input.cpp
|
||||
src/unit-wstring.cpp)
|
||||
|
|
|
|||
126
test/src/unit-udt_macro.cpp
Normal file
126
test/src/unit-udt_macro.cpp
Normal file
|
|
@ -0,0 +1,126 @@
|
|||
/*
|
||||
__ _____ _____ _____
|
||||
__| | __| | | | JSON for Modern C++ (test suite)
|
||||
| | |__ | | | | | | version 3.8.0
|
||||
|_____|_____|_____|_|___| https://github.com/nlohmann/json
|
||||
|
||||
Licensed under the MIT License <http://opensource.org/licenses/MIT>.
|
||||
SPDX-License-Identifier: MIT
|
||||
Copyright (c) 2013-2019 Niels Lohmann <http://nlohmann.me>.
|
||||
|
||||
Permission is hereby granted, free of charge, to any person obtaining a copy
|
||||
of this software and associated documentation files (the "Software"), to deal
|
||||
in the Software without restriction, including without limitation the rights
|
||||
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
||||
copies of the Software, and to permit persons to whom the Software is
|
||||
furnished to do so, subject to the following conditions:
|
||||
|
||||
The above copyright notice and this permission notice shall be included in all
|
||||
copies or substantial portions of the Software.
|
||||
|
||||
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
||||
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
||||
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
||||
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
||||
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
||||
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
||||
SOFTWARE.
|
||||
*/
|
||||
|
||||
#include "doctest_compatibility.h"
|
||||
|
||||
#include <nlohmann/json.hpp>
|
||||
using nlohmann::json;
|
||||
|
||||
#include <utility>
|
||||
|
||||
namespace persons
|
||||
{
|
||||
class person_with_private_data
|
||||
{
|
||||
private:
|
||||
std::string name;
|
||||
int age = 0;
|
||||
|
||||
public:
|
||||
bool operator==(const person_with_private_data& rhs) const
|
||||
{
|
||||
return std::tie(name, age) == std::tie(rhs.name, rhs.age);
|
||||
}
|
||||
|
||||
person_with_private_data() = default;
|
||||
person_with_private_data(std::string name, int age)
|
||||
: name(std::move(name))
|
||||
, age(age)
|
||||
{}
|
||||
|
||||
NLOHMANN_DEFINE_TYPE_INTRUSIVE(person_with_private_data, age, name);
|
||||
};
|
||||
|
||||
class person_without_private_data_1
|
||||
{
|
||||
public:
|
||||
std::string name;
|
||||
int age = 0;
|
||||
|
||||
bool operator==(const person_without_private_data_1& rhs) const
|
||||
{
|
||||
return std::tie(name, age) == std::tie(rhs.name, rhs.age);
|
||||
}
|
||||
|
||||
person_without_private_data_1() = default;
|
||||
person_without_private_data_1(std::string name, int age)
|
||||
: name(std::move(name))
|
||||
, age(age)
|
||||
{}
|
||||
|
||||
NLOHMANN_DEFINE_TYPE_INTRUSIVE(person_without_private_data_1, age, name);
|
||||
};
|
||||
|
||||
class person_without_private_data_2
|
||||
{
|
||||
public:
|
||||
std::string name;
|
||||
int age = 0;
|
||||
|
||||
bool operator==(const person_without_private_data_2& rhs) const
|
||||
{
|
||||
return std::tie(name, age) == std::tie(rhs.name, rhs.age);
|
||||
}
|
||||
|
||||
person_without_private_data_2() = default;
|
||||
person_without_private_data_2(std::string name, int age)
|
||||
: name(std::move(name))
|
||||
, age(age)
|
||||
{}
|
||||
};
|
||||
|
||||
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person_without_private_data_2, age, name);
|
||||
} // namespace persons
|
||||
|
||||
TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRUSIVE", T,
|
||||
persons::person_with_private_data,
|
||||
persons::person_without_private_data_1,
|
||||
persons::person_without_private_data_2)
|
||||
{
|
||||
SECTION("person")
|
||||
{
|
||||
// serialization
|
||||
T p1("Erik", 1);
|
||||
CHECK(json(p1).dump() == "{\"age\":1,\"name\":\"Erik\"}");
|
||||
|
||||
// deserialization
|
||||
T p2 = json(p1);
|
||||
CHECK(p2 == p1);
|
||||
|
||||
// roundtrip
|
||||
CHECK(T(json(p1)) == p1);
|
||||
CHECK(json(T(json(p1))) == json(p1));
|
||||
|
||||
// check exception in case of missing field
|
||||
json j = json(p1);
|
||||
j.erase("age");
|
||||
T p3;
|
||||
CHECK_THROWS_WITH_AS(p3 = json(j), "[json.exception.out_of_range.403] key 'age' not found", json::out_of_range);
|
||||
}
|
||||
}
|
||||
Loading…
Reference in a new issue