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api/basic_json/get.md

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+# <small>nlohmann::basic_json::</small>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;
+
+// (3)
+template<typename PointerType>
+PointerType get_ptr();
+
+template<typename PointerType>
+constexpr const PointerType get_ptr() const noexcept;
+```
+
+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 overload 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 overload 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;
+    ```
+
+3. Explicit pointer access to the internally stored JSON value. No copies are made.
+
+## Template parameters
+
+`ValueType`
+:   the value type to return
+
+`BasicJsonType`
+:   a specialization of `basic_json`
+
+`PointerType`
+:   pointer type; must be a pointer to [`array_t`](array_t.md), [`object_t`](object_t.md), [`string_t`](string_t.md),
+    [`boolean_t`](boolean_t.md), [`number_integer_t`](number_integer_t.md), or
+    [`number_unsigned_t`](number_unsigned_t.md), [`number_float_t`](number_float_t.md), or [`binary_t`](binary_t.md).
+    Other types will not compile.
+
+## Return value
+
+1. copy of the JSON value, converted to `ValueType`
+2. a copy of `#!cpp *this`, converted into `BasicJsonType`
+3. pointer to the internally stored JSON value if the requested pointer type fits to the JSON value; `#!cpp nullptr`
+   otherwise
+
+## Exceptions
+
+Depends on what `json_serializer<ValueType>` `from_json()` method throws
+
+## Complexity
+
+Depends on the `json_serializer<ValueType>::from_json()` implementation for overloads (1) and (2); constant for
+overload (3).
+
+## Notes
+
+!!! danger "Undefined behavior for pointers"
+
+    Writing data to the pointee (overload 3) of the result yields an undefined state.
+
+!!! danger "Undefined behavior for numeric conversions"
+
+    Conversions between numeric types are performed by the corresponding
+    `from_json()` implementation using the target C++ type. When converting
+    between numeric types, the library does not check whether the source
+    value is representable by the target type.
+    
+    If the source value is outside the range of the target type, the behavior
+    is the same as the corresponding C++ conversion. In particular, converting
+    a floating-point value to an integer type that cannot represent the value
+    results in undefined behavior.
+
+    See [Number conversion](../../features/types/number_handling.md#number-conversion)
+    for more information.
+
+## Examples
+
+??? 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"
+    ```
+
+??? example
+
+    The example below shows how pointers to internal values of a JSON value can be requested. Note that no type
+    conversions are made and a `#cpp nullptr` is returned if the value and the requested pointer type does not match.
+        
+    ```cpp
+    --8<-- "examples/get__PointerType.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/get__PointerType.output"
+    ```
+
+## See also
+
+- [get_to](get_to.md) convert and write into a passed value
+- [get_ptr](get_ptr.md) get a pointer to the stored value
+- [get_ref](get_ref.md) get a reference to the stored value
+- [operator ValueType](operator_ValueType.md) get a value via implicit conversion
+- [Converting values](../../features/conversions.md) - the type conversions article
+
+## 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.
+3. Since version 1.0.0.