5352856f04
* Add key_compare member to ordered_map
* Replace == with key_compare in ordered_map
* Expose the actual comparison function used by object_t
nlohmann::ordered_map uses a different comparison function than the one
provided via template parameter.
* Introduce a type trait to detect if object_t has a key_compare member.
* Rename object_comparator_t to default_object_comparator_t.
* Add object_comparator_t to be conditionally defined as
object_t::key_compare, if available, or default_object_comparator_t
otherwise.
* Update the documentation accordingly.
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
* Add type traits to check if a type is usable as object key
Add type trait to check:
* if a type is a specialization of a template.
* if a type is a json_pointer.
* if a type is a basic_json::{const_,}iterator.
* if two types are comparable using a given comparison functor.
* if a type is comparable to basic_json::object_t::key_type.
* if a type has a member type is_transparent.
* if a type is usable as object key.
* if a type has an erase() function accepting a given KeyType.
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
* Rework basic_json element access to accept more key types
Rework basic_json element access member functions and operators to
accept any type that meets the requirements defined by type trait
detail::is_usable_as_key_type.
Member functions and operators:
* at()
* operator[]
* value()
* erase()
* find()
* count()
* contains()
Update documentation to reflect these changes.
Add unit tests to excercise the new functions using std::string_view.
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
73 lines
1.8 KiB
Markdown
73 lines
1.8 KiB
Markdown
# <small>nlohmann::basic_json::</small>find
|
|
|
|
```cpp
|
|
// (1)
|
|
iterator find(const typename object_t::key_type& key);
|
|
const_iterator find(const typename object_t::key_type& key) const;
|
|
|
|
// (2)
|
|
template<typename KeyType>
|
|
iterator find(KeyType&& key);
|
|
template<typename KeyType>
|
|
const_iterator find(KeyType&& key) const;
|
|
```
|
|
|
|
1. Finds an element in a JSON object with a key equivalent to `key`. If the element is not found or the
|
|
JSON value is not an object, `end()` is returned.
|
|
2. See 1. This overload is only available if `KeyType` is comparable with `#!cpp typename object_t::key_type` and
|
|
`#!cpp typename object_comparator_t::is_transparent` denotes a type.
|
|
|
|
## Template parameters
|
|
|
|
`KeyType`
|
|
: A type for an object key other than [`json_pointer`](../json_pointer/index.md) that is comparable with
|
|
[`string_t`](string_t.md) using [`object_comparator_t`](object_comparator_t.md).
|
|
This can also be a string view (C++17).
|
|
|
|
## Parameters
|
|
|
|
`key` (in)
|
|
: key value of the element to search for.
|
|
|
|
## Return value
|
|
|
|
Iterator to an element with a key equivalent to `key`. If no such element is found or the JSON value is not an object,
|
|
a past-the-end iterator (see `end()`) 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 `end()` when executed on a JSON type that is not an object.
|
|
|
|
## Examples
|
|
|
|
??? example
|
|
|
|
The example shows how `find()` is used.
|
|
|
|
```cpp
|
|
--8<-- "examples/find__key_type.cpp"
|
|
```
|
|
|
|
Output:
|
|
|
|
```json
|
|
--8<-- "examples/find__key_type.output"
|
|
```
|
|
|
|
## See also
|
|
|
|
- [contains](contains.md) checks whether a key exists
|
|
|
|
## Version history
|
|
|
|
1. Added in version 3.11.0.
|
|
2. Added in version 1.0.0. Changed to support comparable types in version 3.11.0.
|