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json/api/basic_json/object_comparator_t.md
2026-09-15 20:47:46 +00:00

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# <small>nlohmann::basic_json::</small>object_comparator_t
```cpp
using object_comparator_t = typename object_t::key_compare;
// or
using object_comparator_t = default_object_comparator_t;
```
The comparator used by [`object_t`](object_t.md). Defined as `#!cpp typename object_t::key_compare` if available,
and [`default_object_comparator_t`](default_object_comparator_t.md) otherwise.
## Examples
??? example
The example below demonstrates the used object comparator.
```cpp
--8<-- "examples/object_comparator_t.cpp"
```
Output:
```json
--8<-- "examples/object_comparator_t.output"
```
## Version history
- Added in version 3.0.0.
- Changed to be conditionally defined as `#!cpp typename object_t::key_compare` or `default_object_comparator_t` in
version 3.11.0.
- Fixed the fallback to `default_object_comparator_t`, which previously failed to compile for object types without a
`key_compare` member type, in version 3.13.0.