Use get instead of template get in REAMD.md and docs in non-template context (#4846)

Signed-off-by: Andy Choi <ccpong516@gmail.com>
This commit is contained in:
Andy Choi
2025-10-30 17:23:04 +08:00
committed by GitHub
parent a6a92c19bf
commit cda9c1e3bd
23 changed files with 81 additions and 81 deletions

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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"].template get<std::string>(),
j["address"].template get<std::string>(),
j["age"].template get<int>()
j["name"].get<std::string>(),
j["address"].get<std::string>(),
j["age"].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.template get<ns::person>();
auto p2 = j.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 `template get<your_type>()` or `get_to(your_type&)`, the `from_json` method will be called.
Likewise, when calling `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 [#1108](https://github.com/nlohmann/json/issues/1108) for errors that may occur otherwise.
* 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.)
* 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.)
* 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.
@@ -191,7 +191,7 @@ struct adl_serializer<boost::optional<T>> {
if (j.is_null()) {
opt = boost::none;
} else {
opt = j.template get<T>(); // same as above, but with
opt = j.get<T>(); // same as above, but with
// adl_serializer<T>::from_json
}
}
@@ -224,7 +224,7 @@ 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.template get<int>()};
return {j.get<int>()};
}
// Here's the catch! You must provide a to_json method! Otherwise, you
@@ -288,7 +288,7 @@ struct bad_serializer
static void from_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 template get<T>(); // oops!
value = j.template get<T>(); // oops!
}
};
```

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

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@@ -235,9 +235,9 @@ integers, and between integers and floating-point values to integers. This behav
!!! 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.template 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.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.template get<std::int64_t>();
std::int64_t i = jd.get<std::int64_t>();
// ...
}
else