mirror of
https://github.com/nlohmann/json.git
synced 2026-10-03 22:06:59 +01:00
47 lines
922 B
Markdown
47 lines
922 B
Markdown
# <small>nlohmann::basic_json::</small>is_null
|
|
|
|
```cpp
|
|
constexpr bool is_null() const noexcept;
|
|
```
|
|
|
|
This function returns `#!cpp true` if and only if the JSON value is `#!json null`.
|
|
|
|
## Return value
|
|
|
|
`#!cpp true` if type is `#!json null`, `#!cpp false` otherwise.
|
|
|
|
## Exception safety
|
|
|
|
No-throw guarantee: this member function never throws exceptions.
|
|
|
|
## Complexity
|
|
|
|
Constant.
|
|
|
|
## Examples
|
|
|
|
??? example
|
|
|
|
The following code exemplifies `is_null()` for all JSON types.
|
|
|
|
```cpp
|
|
--8<-- "examples/is_null.cpp"
|
|
```
|
|
|
|
Output:
|
|
|
|
```json
|
|
--8<-- "examples/is_null.output"
|
|
```
|
|
|
|
## See also
|
|
|
|
- [is_array](is_array.md) checks whether the JSON value is an array
|
|
- [is_object](is_object.md) checks whether the JSON value is an object
|
|
- [type](type.md) returns the type of the JSON value
|
|
- [value_t](value_t.md) the enumeration of JSON types
|
|
|
|
## Version history
|
|
|
|
- Added in version 1.0.0.
|