json/doc/mkdocs/docs/api/basic_json/get.md

basic_json::get

// (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 and DefaultConstructible. The value is converted by calling the json_serializer<ValueType> from_json() method.

   The function is equivalent to executing

   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 and not DefaultConstructible, the value is converted by calling the json_serializer<ValueType> from_json() method.

   The function is then equivalent to executing

   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

   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.