Niels Lohmann
a47170346a
* docs: new design for the documentation site Apply the brand to the Material for MkDocs site: Inter and JetBrains Mono served by the site (upright and real italic), brand colours, blue header band with the syntax pattern, wordmark in the header, new home page (hero, cards, animated feature tour), 404 page, polish for tabs, search, footer, focus rings, tables and code blocks, and theme features (code copy, previous/next footer, TOC follow, search suggestions). Draw the number railroad diagram, the parser callback events and the iterator illustrations as inline SVGs that follow the light and dark scheme. The generator scripts are in docs/mkdocs/scripts/figures; the feature slideshow (json-light.svg, json-dark.svg, replacing json.gif on the home page) is built by docs/mkdocs/scripts/slideshow. Decision nodes in five flowcharts become hexagons, which need far less room. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: add figures, table captions and a macro chooser - Figures with numbered captions: SAX stepper, json_view layout and edit stepper, exception map, JSON pointer and patch walkers, QA pipeline, scaling and binary size charts, roadmap lanes, release timeline, integration decision tree and namespace builder - Table captions (nj-table-caption) on 9 pages - Compile times: modules and PCH charts, filesystem section, re-measured Figure 1, links between features/modules.md and compile_times.md - Interactive macro chooser for features/arbitrary_types.md - Link check: exclude URLs that answer the plugin with 400/401/419 or are dead (customers.md) Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: macro chooser generates adl_serializer for non-default-constructible types Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: cross-link concept pages and API pages in See also sections Add See also links in both directions between the concept pages (features, home, integration) and the API pages, write API links in code font, give every entry a comment after a dash, and show the callback event figure on the parser callbacks page. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: address review comments on the new design - Home: add a "Latest release" button - Sponsors: update the list and group it by tier - Features: list all feature pages on the index page - Releases: add highlights per release, link the 4.0 roadmap, add the first commit to the timeline - Exceptions: prefix all example messages with the exception name - API: no code font for format names in the See also links of the to_/from_ pages - Merge Patch: show the document before, the patch, and the result - Replace "--" with typographic dashes, mark external links with an icon, center Mermaid diagrams Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me>
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format_as(basic_json)
template <typename BasicJsonType>
std::string format_as(const BasicJsonType& j);
This function implements the format_as
customization point used by the {fmt} library (fmtlib). It has no
dependency on any fmt header and no effect at all unless a caller's translation unit also includes
fmt and calls fmt::format/fmt::print on a JSON value.
Template parameters
BasicJsonType- a specialization of
basic_json
Return value
string containing the serialization of the JSON value (same as dump())
Exception safety
Strong guarantee: if an exception is thrown, there are no changes to any JSON value.
Exceptions
Throws type_error.316 if a string stored inside the JSON value
is not UTF-8 encoded
Complexity
Linear.
Possible implementation
template <typename BasicJsonType>
std::string format_as(const BasicJsonType& j)
{
return j.dump();
}
Notes
!!! warning "Version-dependent effect on fmt"
`fmt` only picks up a `format_as` overload that returns a `std::string` in fmt **10.0.0 through
11.0.2**. Starting with fmt **11.1.0**, `fmt` restricts automatic `format_as` pickup to overloads that
return an arithmetic type, so this function has no effect there (it is simply unused, not a compile
error).
If you use fmt \>= 11.1.0, or want the same pretty-print spec support that
[`std::formatter<basic_json>`](std_formatter.md) has (`#!cpp "{:#}"`, a width to set the indent such
as `#!cpp "{:2}"`/`#!cpp "{:#2}"`, and fill-and-align to pick the indent character such as
`#!cpp "{:.>#}"`), define your own `fmt::formatter` specialization mirroring the same logic:
```cpp
--8<-- "../../../tests/fmt_formatter/project/main.cpp:formatter_recipe"
```
This recipe isn't shipped by the library itself, since doing so would make `fmt` a build dependency
(see the FAQ entry on
[using JSON values with `std::format` or `fmt`](../../home/faq.md#using-json-values-with-stdformat-or-fmt)
for more background) — but it *is* compiled and exercised against a real, current `fmt` release as
part of the library's own test suite (`tests/fmt_formatter`, via CMake `FetchContent`), so it's kept in
sync with `std::formatter<basic_json>` and verified to actually work, not just illustrative.
Examples
??? example
The following code shows how the library's `format_as()` function integrates with `fmt::format`,
allowing argument-dependent lookup.
```cpp
--8<-- "examples/format_as.cpp"
```
Output:
```json
--8<-- "examples/format_as.output"
```
See also
dump- serialize a JSON value to a stringstd::formatter<basic_json>- thestd::format(C++20) equivalent- Serialization - the serialization article
Version history
- Added in version 3.13.0.