1.1 KiB
1.1 KiB
basic_json::contains
template<typename KeyT>
bool contains(KeyT && key) const;
Check whether an element exists in a JSON object with key equivalent to key. If the element is not found or the JSON
value is not an object, #!cpp false is returned.
Template parameters
KeyT- A type for an object key other than
basic_json::json_pointer.
Parameters
key(in)- key value to check its existence.
Return value
#!cpp true if an element with specified key exists. If no such element with such key is found or the JSON value is
not an object, #!cpp false is returned.
Exception safety
Strong exception safety: if an exception occurs, the original value stays intact.
Complexity
Logarithmic in the size of the JSON object.
Notes
This method always returns #!cpp false when executed on a JSON type that is not an object.
Example
??? example
The example shows how `contains()` is used.
```cpp
--8<-- "examples/contains.cpp"
```
Output:
```json
--8<-- "examples/contains.output"
```
Version history
- Added in version 3.6.0.