Niels Lohmann
52b72b5684
- Make the iterator range illustrations legible in dark mode (prefers-color-scheme rules inside the SVGs). - Add a "Byte layout" section with a color-coded byte table to each binary format page (BJData, BON8, BSON, CBOR, MessagePack, UBJSON), and highlight the smallest size per file in the comparison table. - Add "See also" sections to the overview pages that lacked one. - Split the release notes into one page per release, grouped by minor version on the overview page, with an "API changes" section per release generated from the API pages' version histories (hooks/api_changes.py). - Fact-check the release notes and version histories against the release tags and correct wrong or misleading entries (e.g., json_serializer 2.1.0, merge_patch 3.1.0, items, count, operator[], to_bjdata, std::string_view key support). Signed-off-by: Niels Lohmann <mail@nlohmann.me>
1.3 KiB
1.3 KiB
nlohmann::ordered_json
using ordered_json = basic_json<ordered_map>;
This type preserves the insertion order of object keys.
Iterator invalidation
The type is based on ordered_map which in turn uses a std::vector to store object elements.
Therefore, adding object elements can yield a reallocation in which case all iterators (including the
end() iterator) and all references to the elements are invalidated. Also, any iterator or
reference after the insertion point will point to the same index, which is now a different value.
Complexity
ordered_map has no lookup index: every key-based object operation is a linear scan, so building or
parsing an object of n keys costs O(n²) rather than O(n log n). See
ordered_map complexity for the per-operation table and for measured numbers.
Examples
??? example
The example below demonstrates how `ordered_json` preserves the insertion order of object keys.
```cpp
--8<-- "examples/ordered_json.cpp"
```
Output:
```json
--8<-- "examples/ordered_json.output"
```
See also
Version history
Added in version 3.9.0.