mirror of
https://github.com/nlohmann/json.git
synced 2026-10-09 16:07:14 +00:00
deploy: 7c9208bfb3
This commit is contained in:
nlohmann committed
1 parent
9a231845c2
commit
279d757031
758 files changed
+56489
-503
No files matched your search
@@ -84,4 +84,4 @@
|
||||
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=n>j_str</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span>
|
||||
<span class=p>}</span>
|
||||
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=p>{</span><span class=nt>"one"</span><span class=p>:</span><span class=mi>1</span><span class=p>,</span><span class=nt>"two"</span><span class=p>:</span><span class=mi>2</span><span class=p>}</span>
|
||||
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li><a href=../dump/ >dump</a></li> <li><a href=../std_formatter/ >std::formatter<basic_json></a> - the <code>std::format</code> (C++20) equivalent</li> <li><a href=../../../features/serialization/ >Serialization</a> - the serialization article</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">¶</a></h2> <ul> <li>Added in version 3.12.x.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 4, 2026 09:13:25 UTC">July 4, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 384 512"><Line truncated
|
||||
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li><a href=../dump/ >dump</a></li> <li><a href=../std_formatter/ >std::formatter<basic_json></a> - the <code>std::format</code> (C++20) equivalent</li> <li><a href=../../../features/serialization/ >Serialization</a> - the serialization article</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">¶</a></h2> <ul> <li>Added in version 3.12.x.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 8, 2026 18:18:24 UTC">July 8, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 384 512"><Line truncated
|
||||
@@ -0,0 +1,154 @@
|
||||
# format_as(basic_json)
|
||||
|
||||
```
|
||||
template <typename BasicJsonType>
|
||||
std::string format_as(const BasicJsonType& j);
|
||||
```
|
||||
|
||||
This function implements the [`format_as`](https://fmt.dev/latest/api/#formatting-user-defined-types) customization point used by the [{fmt}](https://github.com/fmtlib/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`](https://json.nlohmann.me/api/basic_json/index.md)
|
||||
|
||||
## Return value
|
||||
|
||||
string containing the serialization of the JSON value (same as [`dump()`](https://json.nlohmann.me/api/basic_json/dump/index.md))
|
||||
|
||||
## Exception safety
|
||||
|
||||
Strong guarantee: if an exception is thrown, there are no changes to any JSON value.
|
||||
|
||||
## Exceptions
|
||||
|
||||
Throws [`type_error.316`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) 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
|
||||
|
||||
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>`](https://json.nlohmann.me/api/basic_json/std_formatter/index.md) has (`"{:#}"`, a width to set the indent such as `"{:2}"`/`"{:#2}"`, and fill-and-align to pick the indent character such as `"{:.>#}"`), define your own `fmt::formatter` specialization mirroring the same logic:
|
||||
|
||||
```
|
||||
template <>
|
||||
struct fmt::formatter<nlohmann::json>
|
||||
{
|
||||
// -1 means compact output (dump()); any value >= 0 means pretty-printed
|
||||
// output with that many spaces (or indent_char) per level.
|
||||
int indent = -1;
|
||||
char indent_char = ' ';
|
||||
|
||||
constexpr auto parse(format_parse_context& ctx) -> format_parse_context::iterator
|
||||
{
|
||||
auto it = ctx.begin();
|
||||
const auto end = ctx.end();
|
||||
constexpr auto is_align = [](char c)
|
||||
{
|
||||
return c == '<' || c == '>' || c == '^';
|
||||
};
|
||||
|
||||
// [[fill] align] - repurposed here to pick a custom indent character
|
||||
if (it != end && it + 1 != end && is_align(it[1]))
|
||||
{
|
||||
indent_char = *it;
|
||||
it += 2;
|
||||
}
|
||||
else if (it != end && is_align(*it))
|
||||
{
|
||||
++it;
|
||||
}
|
||||
|
||||
// ['#'] - "alternate form", used here to request pretty-printing with a
|
||||
// default indent of 4 (overridden by an explicit width below, if given)
|
||||
if (it != end && *it == '#')
|
||||
{
|
||||
indent = 4;
|
||||
++it;
|
||||
}
|
||||
|
||||
// [width] - repurposed here to pick the indent size; a width without '#'
|
||||
// implies pretty-printing since an indent otherwise has no meaning
|
||||
if (it != end && *it >= '1' && *it <= '9')
|
||||
{
|
||||
indent = 0;
|
||||
while (it != end && *it >= '0' && *it <= '9')
|
||||
{
|
||||
indent = (indent * 10) + (*it - '0');
|
||||
++it;
|
||||
}
|
||||
}
|
||||
|
||||
if (it != end && *it != '}')
|
||||
{
|
||||
throw fmt::format_error("invalid format args for nlohmann::json");
|
||||
}
|
||||
|
||||
return it;
|
||||
}
|
||||
|
||||
auto format(const nlohmann::json& j, format_context& ctx) const
|
||||
{
|
||||
const auto dumped = j.dump(indent, indent_char);
|
||||
return fmt::format_to(ctx.out(), "{}", dumped);
|
||||
}
|
||||
};
|
||||
```
|
||||
|
||||
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`](https://json.nlohmann.me/home/faq/#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.
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <nlohmann/json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
// create a JSON value
|
||||
json j = {{"one", 1}, {"two", 2}};
|
||||
|
||||
// format_as() is found via argument-dependent lookup, the same way
|
||||
// fmt::format/fmt::print would find it
|
||||
auto j_str = format_as(j);
|
||||
|
||||
std::cout << j_str << std::endl;
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
{"one":1,"two":2}
|
||||
```
|
||||
|
||||
## See also
|
||||
|
||||
- [dump](https://json.nlohmann.me/api/basic_json/dump/index.md)
|
||||
- [std::formatter](https://json.nlohmann.me/api/basic_json/std_formatter/index.md) - the `std::format` (C++20) equivalent
|
||||
- [Serialization](https://json.nlohmann.me/features/serialization/index.md) - the serialization article
|
||||
|
||||
## Version history
|
||||
|
||||
- Added in version 3.12.x.
|
||||
Reference in new issue
Block a user