📝 add more API documentation

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Niels Lohmann 2020-08-14 13:47:54 +02:00
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4 changed files with 104 additions and 5 deletions

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@ -32,7 +32,12 @@ INSERT INTO searchIndex(name, type, path) VALUES ('error_handler_t', 'Enum', 'ap
INSERT INTO searchIndex(name, type, path) VALUES ('exception', 'Class', 'api/basic_json/exception/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('find', 'Method', 'api/basic_json/find/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('flatten', 'Method', 'api/basic_json/flatten/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('from_bson', 'Function', 'api/basic_json/from_bson/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('from_cbor', 'Function', 'api/basic_json/from_cbor/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('from_msgpack', 'Function', 'api/basic_json/from_msgpack/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('from_ubjson', 'Function', 'api/basic_json/from_ubjson/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('front', 'Method', 'api/basic_json/front/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('get', 'Method', 'api/basic_json/get/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('get_allocator', 'Function', 'api/basic_json/get_allocator/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('input_format_t', 'Enum', 'api/basic_json/input_format_t/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('insert', 'Method', 'api/basic_json/insert/index.html');
@ -89,10 +94,6 @@ INSERT INTO searchIndex(name, type, path) VALUES ('type_error', 'Class', 'api/ba
INSERT INTO searchIndex(name, type, path) VALUES ('type_name', 'Method', 'api/basic_json/type_name/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('unflatten', 'Method', 'api/basic_json/unflatten/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('update', 'Method', 'api/basic_json/update/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('from_bson', 'Function', 'api/basic_json/from_bson/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('from_cbor', 'Function', 'api/basic_json/from_cbor/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('from_msgpack', 'Function', 'api/basic_json/from_msgpack/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('from_ubjson', 'Function', 'api/basic_json/from_ubjson/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('to_bson', 'Function', 'api/basic_json/to_bson/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('to_cbor', 'Function', 'api/basic_json/to_cbor/index.html');
INSERT INTO searchIndex(name, type, path) VALUES ('to_msgpack', 'Function', 'api/basic_json/to_msgpack/index.html');

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@ -0,0 +1,97 @@
# basic_json::get
```cpp
// (1)
template<typename ValueType>
ValueType get() const noexcept(
noexcept(JSONSerializer<ValueType>::from_json(
std::declval<const basic_json_t&>(), std::declval<ValueType&>())));
// (2)
template<typename BasicJsonType>
BasicJsonType get() const;
```
1. Explicit type conversion between the JSON value and a compatible value which is
[CopyConstructible](https://en.cppreference.com/w/cpp/named_req/CopyConstructible) and
[DefaultConstructible](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible). The value is converted by
calling the `json_serializer<ValueType>` `from_json()` method.
The function is equivalent to executing
```cpp
ValueType ret;
JSONSerializer<ValueType>::from_json(*this, ret);
return ret;
```
This overloads is chosen if:
- `ValueType` is not `basic_json`,
- `json_serializer<ValueType>` has a `from_json()` method of the form
`void from_json(const basic_json&, ValueType&)`, and
- `json_serializer<ValueType>` does not have a `from_json()` method of the form
`ValueType from_json(const basic_json&)`
If the type is **not** [CopyConstructible](https://en.cppreference.com/w/cpp/named_req/CopyConstructible) and
**not** [DefaultConstructible](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible), the value is
converted by calling the `json_serializer<ValueType>` `from_json()` method.
The function is then equivalent to executing
```cpp
return JSONSerializer<ValueTypeCV>::from_json(*this);
```
This overloads is chosen if:
- `ValueType` is not `basic_json` and
- `json_serializer<ValueType>` has a `from_json()` method of the form
`ValueType from_json(const basic_json&)`
If `json_serializer<ValueType>` has both overloads of `from_json()`, the latter one is chosen.
2. Overload for `basic_json` specializations. The function is equivalent to executing
```cpp
return *this;
```
## Template parameters
`ValueType`
: the value type to return
`BasicJsonType`
: a specialization of `basic_json`
## Return value
1. copy of the JSON value, converted to `ValueType`
2. a copy of `#!cpp *this`, converted into `BasicJsonType`
## Exceptions
Depends on what `json_serializer<ValueType>` `from_json()` method throws
## Example
??? example
The example below shows several conversions from JSON values
to other types. There a few things to note: (1) Floating-point numbers can
be converted to integers, (2) A JSON array can be converted to a standard
`std::vector<short>`, (3) A JSON object can be converted to C++
associative containers such as `std::unordered_map<std::string, json>`.
```cpp
--8<-- "examples/get__ValueType_const.cpp"
```
Output:
```json
--8<-- "examples/get__ValueType_const.output"
```
## Version history
1. Since version 2.1.0.
2. Since version 2.1.0. Extended to work with other specializations of `basic_json` in version 3.2.0.

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@ -135,7 +135,7 @@ Functions to inspect the type of a JSON value.
Direct access to the stored value of a JSON value.
- get - get a value
- [**get**](get.md) - get a value
- get_to - get a value
- get_ptr - get a pointer value
- get_ref - get a reference value

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@ -106,6 +106,7 @@ nav:
- api/basic_json/from_msgpack.md
- api/basic_json/from_ubjson.md
- api/basic_json/front.md
- api/basic_json/get.md
- api/basic_json/get_allocator.md
- api/basic_json/input_format_t.md
- api/basic_json/insert.md