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Use template get instead of get in examples (#4039) 

Co-authored-by: tusooa <tusooa@kazv.moe>
pull/3996/head
No 2023-06-11 04:06:24 -04:00 committed by GitHub
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36
README.md
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@ -301,7 +301,7 @@ Note the difference between serialization and assignment:
json j_string = "this is a string";
// retrieve the string value
auto cpp_string = j_string.get<std::string>();
auto cpp_string = j_string.template get<std::string>();
// retrieve the string value (alternative when a variable already exists)
std::string cpp_string2;
j_string.get_to(cpp_string2);
@ -310,7 +310,7 @@ j_string.get_to(cpp_string2);
std::string serialized_string = j_string.dump();
// output of original string
std::cout << cpp_string << " == " << cpp_string2 << " == " << j_string.get<std::string>() << '\n';
std::cout << cpp_string << " == " << cpp_string2 << " == " << j_string.template get<std::string>() << '\n';
// output of serialized value
std::cout << j_string << " == " << serialized_string << std::endl;
```
@ -483,7 +483,7 @@ for (auto& element : j) {
}
// getter/setter
const auto tmp = j[0].get<std::string>();
const auto tmp = j[0].template get<std::string>();
j[1] = 42;
bool foo = j.at(2);
@ -691,7 +691,7 @@ You can switch off implicit conversions by defining `JSON_USE_IMPLICIT_CONVERSIO
// strings
std::string s1 = "Hello, world!";
json js = s1;
auto s2 = js.get<std::string>();
auto s2 = js.template get<std::string>();
// NOT RECOMMENDED
std::string s3 = js;
std::string s4;
@ -700,7 +700,7 @@ s4 = js;
// Booleans
bool b1 = true;
json jb = b1;
auto b2 = jb.get<bool>();
auto b2 = jb.template get<bool>();
// NOT RECOMMENDED
bool b3 = jb;
bool b4;
@ -709,7 +709,7 @@ b4 = jb;
// numbers
int i = 42;
json jn = i;
auto f = jn.get<double>();
auto f = jn.template get<double>();
// NOT RECOMMENDED
double f2 = jb;
double f3;
@ -752,9 +752,9 @@ j["age"] = p.age;
// convert from JSON: copy each value from the JSON object
ns::person p {
j["name"].get<std::string>(),
j["address"].get<std::string>(),
j["age"].get<int>()
j["name"].template get<std::string>(),
j["address"].template get<std::string>(),
j["age"].template get<int>()
};
```
@ -771,7 +771,7 @@ std::cout << j << std::endl;
// {"address":"744 Evergreen Terrace","age":60,"name":"Ned Flanders"}
// conversion: json -> person
auto p2 = j.get<ns::person>();
auto p2 = j.template get<ns::person>();
// that's it
assert(p == p2);
@ -798,13 +798,13 @@ namespace ns {
```
That's all! When calling the `json` constructor with your type, your custom `to_json` method will be automatically called.
Likewise, when calling `get<your_type>()` or `get_to(your_type&)`, the `from_json` method will be called.
Likewise, when calling `template get<your_type>()` or `get_to(your_type&)`, the `from_json` method will be called.
Some important things:
* Those methods **MUST** be in your type's namespace (which can be the global namespace), or the library will not be able to locate them (in this example, they are in namespace `ns`, where `person` is defined).
* Those methods **MUST** be available (e.g., proper headers must be included) everywhere you use these conversions. Look at [issue 1108](https://github.com/nlohmann/json/issues/1108) for errors that may occur otherwise.
* When using `get<your_type>()`, `your_type` **MUST** be [DefaultConstructible](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible). (There is a way to bypass this requirement described later.)
* When using `template get<your_type>()`, `your_type` **MUST** be [DefaultConstructible](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible). (There is a way to bypass this requirement described later.)
* In function `from_json`, use function [`at()`](https://json.nlohmann.me/api/basic_json/at/) 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.
@ -889,8 +889,8 @@ namespace nlohmann {
if (j.is_null()) {
opt = boost::none;
} else {
opt = j.get<T>(); // same as above, but with
// adl_serializer<T>::from_json
opt = j.template get<T>(); // same as above, but with
// adl_serializer<T>::from_json
}
}
};
@ -917,7 +917,7 @@ namespace nlohmann {
// note: the return type is no longer 'void', and the method only takes
// one argument
static move_only_type from_json(const json& j) {
return {j.get<int>()};
return {j.template get<int>()};
}
// Here's the catch! You must provide a to_json method! Otherwise, you
@ -1021,11 +1021,11 @@ assert(j == "stopped");
// json string to enum
json j3 = "running";
assert(j3.get<TaskState>() == TS_RUNNING);
assert(j3.template get<TaskState>() == TS_RUNNING);
// undefined json value to enum (where the first map entry above is the default)
json jPi = 3.14;
assert(jPi.get<TaskState>() == TS_INVALID );
assert(jPi.template get<TaskState>() == TS_INVALID );
```
Just as in [Arbitrary Type Conversions](#arbitrary-types-conversions) above,
@ -1033,7 +1033,7 @@ Just as in [Arbitrary Type Conversions](#arbitrary-types-conversions) above,
- It MUST be available (e.g., proper headers must be included) everywhere you use the conversions.
Other Important points:
- When using `get<ENUM_TYPE>()`, undefined JSON values will default to the first pair specified in your map. Select this default pair carefully.
- When using `template get<ENUM_TYPE>()`, undefined JSON values will default to the first pair specified in your map. Select this default pair carefully.
- If an enum or JSON value is specified more than once in your map, the first matching occurrence from the top of the map will be returned when converting to or from JSON.
### Binary formats (BSON, CBOR, MessagePack, UBJSON, and BJData)

2
docs/examples/from_json__default_constructible.cpp
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@ -31,7 +31,7 @@ int main()
j["address"] = "744 Evergreen Terrace";
j["age"] = 60;
auto p = j.get<ns::person>();
auto p = j.template get<ns::person>();
std::cout << p.name << " (" << p.age << ") lives in " << p.address << std::endl;
}

2
docs/examples/from_json__non_default_constructible.cpp
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@ -47,7 +47,7 @@ int main()
j["address"] = "744 Evergreen Terrace";
j["age"] = 60;
auto p = j.get<ns::person>();
auto p = j.template get<ns::person>();
std::cout << p.name << " (" << p.age << ") lives in " << p.address << std::endl;
}

10
docs/examples/get__PointerType.cpp
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@ -9,11 +9,11 @@ int main()
json value = 17;
// explicitly getting pointers
auto p1 = value.get<const json::number_integer_t*>();
auto p2 = value.get<json::number_integer_t*>();
auto p3 = value.get<json::number_integer_t* const>();
auto p4 = value.get<const json::number_integer_t* const>();
auto p5 = value.get<json::number_float_t*>();
auto p1 = value.template get<const json::number_integer_t*>();
auto p2 = value.template get<json::number_integer_t*>();
auto p3 = value.template get<json::number_integer_t* const>();
auto p4 = value.template get<const json::number_integer_t* const>();
auto p5 = value.template get<json::number_float_t*>();
// print the pointees
std::cout << *p1 << ' ' << *p2 << ' ' << *p3 << ' ' << *p4 << '\n';

16
docs/examples/get__ValueType_const.cpp
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@ -22,14 +22,14 @@ int main()
};
// use explicit conversions
auto v1 = json_types["boolean"].get<bool>();
auto v2 = json_types["number"]["integer"].get<int>();
auto v3 = json_types["number"]["integer"].get<short>();
auto v4 = json_types["number"]["floating-point"].get<float>();
auto v5 = json_types["number"]["floating-point"].get<int>();
auto v6 = json_types["string"].get<std::string>();
auto v7 = json_types["array"].get<std::vector<short>>();
auto v8 = json_types.get<std::unordered_map<std::string, json>>();
auto v1 = json_types["boolean"].template get<bool>();
auto v2 = json_types["number"]["integer"].template get<int>();
auto v3 = json_types["number"]["integer"].template get<short>();
auto v4 = json_types["number"]["floating-point"].template get<float>();
auto v5 = json_types["number"]["floating-point"].template get<int>();
auto v6 = json_types["string"].template get<std::string>();
auto v7 = json_types["array"].template get<std::vector<short>>();
auto v8 = json_types.template get<std::unordered_map<std::string, json>>();
// print the conversion results
std::cout << v1 << '\n';

4
docs/examples/nlohmann_define_type_intrusive_explicit.cpp
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@ -45,13 +45,13 @@ int main()
// deserialization: json -> person
json j2 = R"({"address": "742 Evergreen Terrace", "age": 40, "name": "Homer Simpson"})"_json;
auto p2 = j2.get<ns::person>();
auto p2 = j2.template get<ns::person>();
// incomplete deserialization:
json j3 = R"({"address": "742 Evergreen Terrace", "name": "Maggie Simpson"})"_json;
try
{
auto p3 = j3.get<ns::person>();
auto p3 = j3.template get<ns::person>();
}
catch (json::exception& e)
{

4
docs/examples/nlohmann_define_type_intrusive_macro.cpp
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@ -33,13 +33,13 @@ int main()
// deserialization: json -> person
json j2 = R"({"address": "742 Evergreen Terrace", "age": 40, "name": "Homer Simpson"})"_json;
auto p2 = j2.get<ns::person>();
auto p2 = j2.template get<ns::person>();
// incomplete deserialization:
json j3 = R"({"address": "742 Evergreen Terrace", "name": "Maggie Simpson"})"_json;
try
{
auto p3 = j3.get<ns::person>();
auto p3 = j3.template get<ns::person>();
}
catch (json::exception& e)
{

4
docs/examples/nlohmann_define_type_intrusive_with_default_explicit.cpp
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@ -46,10 +46,10 @@ int main()
// deserialization: json -> person
json j2 = R"({"address": "742 Evergreen Terrace", "age": 40, "name": "Homer Simpson"})"_json;
auto p2 = j2.get<ns::person>();
auto p2 = j2.template get<ns::person>();
// incomplete deserialization:
json j3 = R"({"address": "742 Evergreen Terrace", "name": "Maggie Simpson"})"_json;
auto p3 = j3.get<ns::person>();
auto p3 = j3.template get<ns::person>();
std::cout << "roundtrip: " << json(p3) << std::endl;
}

4
docs/examples/nlohmann_define_type_intrusive_with_default_macro.cpp
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@ -33,10 +33,10 @@ int main()
// deserialization: json -> person
json j2 = R"({"address": "742 Evergreen Terrace", "age": 40, "name": "Homer Simpson"})"_json;
auto p2 = j2.get<ns::person>();
auto p2 = j2.template get<ns::person>();
// incomplete deserialization:
json j3 = R"({"address": "742 Evergreen Terrace", "name": "Maggie Simpson"})"_json;
auto p3 = j3.get<ns::person>();
auto p3 = j3.template get<ns::person>();
std::cout << "roundtrip: " << json(p3) << std::endl;
}

4
docs/examples/nlohmann_define_type_non_intrusive_explicit.cpp
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@ -38,13 +38,13 @@ int main()
// deserialization: json -> person
json j2 = R"({"address": "742 Evergreen Terrace", "age": 40, "name": "Homer Simpson"})"_json;
auto p2 = j2.get<ns::person>();
auto p2 = j2.template get<ns::person>();
// incomplete deserialization:
json j3 = R"({"address": "742 Evergreen Terrace", "name": "Maggie Simpson"})"_json;
try
{
auto p3 = j3.get<ns::person>();
auto p3 = j3.template get<ns::person>();
}
catch (json::exception& e)
{

4
docs/examples/nlohmann_define_type_non_intrusive_macro.cpp
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@ -26,13 +26,13 @@ int main()
// deserialization: json -> person
json j2 = R"({"address": "742 Evergreen Terrace", "age": 40, "name": "Homer Simpson"})"_json;
auto p2 = j2.get<ns::person>();
auto p2 = j2.template get<ns::person>();
// incomplete deserialization:
json j3 = R"({"address": "742 Evergreen Terrace", "name": "Maggie Simpson"})"_json;
try
{
auto p3 = j3.get<ns::person>();
auto p3 = j3.template get<ns::person>();
}
catch (json::exception& e)
{

4
docs/examples/nlohmann_define_type_non_intrusive_with_default_explicit.cpp
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@ -44,10 +44,10 @@ int main()
// deserialization: json -> person
json j2 = R"({"address": "742 Evergreen Terrace", "age": 40, "name": "Homer Simpson"})"_json;
auto p2 = j2.get<ns::person>();
auto p2 = j2.template get<ns::person>();
// incomplete deserialization:
json j3 = R"({"address": "742 Evergreen Terrace", "name": "Maggie Simpson"})"_json;
auto p3 = j3.get<ns::person>();
auto p3 = j3.template get<ns::person>();
std::cout << "roundtrip: " << json(p3) << std::endl;
}

4
docs/examples/nlohmann_define_type_non_intrusive_with_default_macro.cpp
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@ -31,10 +31,10 @@ int main()
// deserialization: json -> person
json j2 = R"({"address": "742 Evergreen Terrace", "age": 40, "name": "Homer Simpson"})"_json;
auto p2 = j2.get<ns::person>();
auto p2 = j2.template get<ns::person>();
// incomplete deserialization:
json j3 = R"({"address": "742 Evergreen Terrace", "name": "Maggie Simpson"})"_json;
auto p3 = j3.get<ns::person>();
auto p3 = j3.template get<ns::person>();
std::cout << "roundtrip: " << json(p3) << std::endl;
}

8
docs/examples/nlohmann_json_serialize_enum.cpp
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@ -44,16 +44,16 @@ int main()
// deserialization
json j_running = "running";
json j_blue = "blue";
auto running = j_running.get<ns::TaskState>();
auto blue = j_blue.get<ns::Color>();
auto running = j_running.template get<ns::TaskState>();
auto blue = j_blue.template get<ns::Color>();
std::cout << j_running << " -> " << running
<< ", " << j_blue << " -> " << static_cast<int>(blue) << std::endl;
// deserializing undefined JSON value to enum
// (where the first map entry above is the default)
json j_pi = 3.14;
auto invalid = j_pi.get<ns::TaskState>();
auto unknown = j_pi.get<ns::Color>();
auto invalid = j_pi.template get<ns::TaskState>();
auto unknown = j_pi.template get<ns::Color>();
std::cout << j_pi << " -> " << invalid << ", "
<< j_pi << " -> " << static_cast<int>(unknown) << std::endl;
}

4
docs/examples/nlohmann_json_serialize_enum_2.cpp
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@ -26,8 +26,8 @@ int main()
// deserialization
json j_rot = "rot";
auto rot = j_rot.get<ns::Color>();
auto red = j_red.get<ns::Color>();
auto rot = j_rot.template get<ns::Color>();
auto red = j_red.template get<ns::Color>();
std::cout << j_rot << " -> " << static_cast<int>(rot) << std::endl;
std::cout << j_red << " -> " << static_cast<int>(red) << std::endl;
}

2
docs/mkdocs/docs/api/adl_serializer/from_json.md
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@ -37,7 +37,7 @@ Copy of the JSON value, converted to `ValueType`
??? example "Example: (1) Default-constructible type"
The example below shows how a `from_json` function can be implemented for a user-defined type. This function is
called by the `adl_serializer` when `get<ns::person>()` is called.
called by the `adl_serializer` when `template get<ns::person>()` is called.
```cpp
--8<-- "examples/from_json__default_constructible.cpp"

10
docs/mkdocs/docs/api/macros/json_disable_enum_serialization.md
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@ -53,7 +53,7 @@ The default value is `0`.
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>();
Choice ch = j.template get<Choice>();
}
```
@ -86,7 +86,7 @@ The default value is `0`.
const json j = Choice::first;
// uses user-defined from_json function defined by macro
Choice ch = j.get<Choice>();
Choice ch = j.template get<Choice>();
}
```
@ -109,7 +109,7 @@ The default value is `0`.
void from_json(const json& j, Choice& ch)
{
auto value = j.get<std::string>();
auto value = j.template get<std::string>();
if (value == "first")
{
ch = Choice::first;
@ -122,7 +122,7 @@ The default value is `0`.
void to_json(json& j, const Choice& ch)
{
auto value = j.get<std::string>();
auto value = j.template get<std::string>();
if (value == "first")
{
ch = Choice::first;
@ -139,7 +139,7 @@ The default value is `0`.
const json j = Choice::first;
// uses user-defined from_json function
Choice ch = j.get<Choice>();
Choice ch = j.template get<Choice>();
}
```

2
docs/mkdocs/docs/api/macros/json_use_implicit_conversions.md
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@ -46,7 +46,7 @@ By default, implicit conversions are enabled.
```cpp
json j = "Hello, world!";
auto s = j.get<std::string>();
auto s = j.template get<std::string>();
```
## See also

2
docs/mkdocs/docs/api/macros/nlohmann_json_serialize_enum.md
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@ -37,7 +37,7 @@ inline void from_json(const BasicJsonType& j, type& e);
!!! important "Important notes"
- When using [`get<ENUM_TYPE>()`](../basic_json/get.md), undefined JSON values will default to the first specified
- When using [`template get<ENUM_TYPE>()`](../basic_json/get.md), undefined JSON values will default to the first specified
conversion. Select this default pair carefully. See example 1 below.
- If an enum or JSON value is specified in multiple conversions, the first matching conversion from the top of the
list will be returned when converting to or from JSON. See example 2 below.

18
docs/mkdocs/docs/features/arbitrary_types.md
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@ -24,9 +24,9 @@ j["age"] = p.age;
// convert from JSON: copy each value from the JSON object
ns::person p {
j["name"].get<std::string>(),
j["address"].get<std::string>(),
j["age"].get<int>()
j["name"].template get<std::string>(),
j["address"].template get<std::string>(),
j["age"].template get<int>()
};
```
@ -43,7 +43,7 @@ std::cout << j << std::endl;
// {"address":"744 Evergreen Terrace","age":60,"name":"Ned Flanders"}
// conversion: json -> person
auto p2 = j.get<ns::person>();
auto p2 = j.template get<ns::person>();
// that's it
assert(p == p2);
@ -70,13 +70,13 @@ namespace ns {
```
That's all! When calling the `json` constructor with your type, your custom `to_json` method will be automatically called.
Likewise, when calling `get<your_type>()` or `get_to(your_type&)`, the `from_json` method will be called.
Likewise, when calling `template get<your_type>()` or `get_to(your_type&)`, the `from_json` method will be called.
Some important things:
* Those methods **MUST** be in your type's namespace (which can be the global namespace), or the library will not be able to locate them (in this example, they are in namespace `ns`, where `person` is defined).
* Those methods **MUST** be available (e.g., proper headers must be included) everywhere you use these conversions. Look at [issue 1108](https://github.com/nlohmann/json/issues/1108) for errors that may occur otherwise.
* When using `get<your_type>()`, `your_type` **MUST** be [DefaultConstructible](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible). (There is a way to bypass this requirement described later.)
* When using `template get<your_type>()`, `your_type` **MUST** be [DefaultConstructible](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible). (There is a way to bypass this requirement described later.)
* In function `from_json`, use function [`at()`](../api/basic_json/at.md) 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.
@ -171,7 +171,7 @@ struct adl_serializer<boost::optional<T>> {
if (j.is_null()) {
opt = boost::none;
} else {
opt = j.get<T>(); // same as above, but with
opt = j.template get<T>(); // same as above, but with
// adl_serializer<T>::from_json
}
}
@ -204,7 +204,7 @@ namespace nlohmann {
// note: the return type is no longer 'void', and the method only takes
// one argument
static move_only_type from_json(const json& j) {
return {j.get<int>()};
return {j.template get<int>()};
}
// Here's the catch! You must provide a to_json method! Otherwise, you
@ -268,7 +268,7 @@ struct bad_serializer
static void to_json(const BasicJsonType& j, T& value) {
// this calls BasicJsonType::json_serializer<T>::from_json(j, value);
// if BasicJsonType::json_serializer == bad_serializer ... oops!
value = j.template get<T>(); // oops!
value = j.template template get<T>(); // oops!
}
};
```

6
docs/mkdocs/docs/features/enum_conversion.md
View File

@ -36,11 +36,11 @@ assert(j == "stopped");
// json string to enum
json j3 = "running";
assert(j3.get<TaskState>() == TS_RUNNING);
assert(j3.template get<TaskState>() == TS_RUNNING);
// undefined json value to enum (where the first map entry above is the default)
json jPi = 3.14;
assert(jPi.get<TaskState>() == TS_INVALID );
assert(jPi.template get<TaskState>() == TS_INVALID );
```
## Notes
@ -54,7 +54,7 @@ Just as in [Arbitrary Type Conversions](arbitrary_types.md) above,
Other Important points:
- When using `get<ENUM_TYPE>()`, undefined JSON values will default to the first pair specified in your map. Select this
- When using `template get<ENUM_TYPE>()`, undefined JSON values will default to the first pair specified in your map. Select this
default pair carefully.
- If an enum or JSON value is specified more than once in your map, the first matching occurrence from the top of the
map will be returned when converting to or from JSON.

8
docs/mkdocs/docs/features/types/number_handling.md
View File

@ -235,9 +235,9 @@ integers, and between integers and floating-point values to integers. This beha
!!! warning "Unconditional number conversions"
```cpp hl_lines="3"
double d = 42.3; // non-integer double value 42.3
json jd = d; // stores double value 42.3
std::int64_t i = jd.get<std::int64_t>(); // now i==42; no warning or error is produced
double d = 42.3; // non-integer double value 42.3
json jd = d; // stores double value 42.3
std::int64_t i = jd.template get<std::int64_t>(); // now i==42; no warning or error is produced
```
Note the last line with throw a [`json.exception.type_error.302`](../../home/exceptions.md#jsonexceptiontype_error302)
@ -259,7 +259,7 @@ The rationale is twofold:
if (jd.is_number_integer())
{
// if so, do the conversion and use i
std::int64_t i = jd.get<std::int64_t>();
std::int64_t i = jd.template get<std::int64_t>();
// ...
}
else

2
docs/mkdocs/docs/integration/migration_guide.md
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@ -187,7 +187,7 @@ conversions with calls to [`get`](../api/basic_json/get.md), [`get_to`](../api/b
```cpp
nlohmann::json j = "Hello, world!";
auto s = j.get<std::string>();
auto s = j.template get<std::string>();
```
=== "Future-proof (alternative)"