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
@@ -424,4 +424,4 @@
|
||||
"Neptune"
|
||||
]
|
||||
}
|
||||
</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=../accept/ >accept</a> - check if the input is valid <abbr title="JavaScript Object Notation">JSON</abbr></li> <li><a href=../sax_parse/ >sax_parse</a> - parse input using the <abbr title="Simple API for XML">SAX</abbr> interface</li> <li><a href=../../operator_gtgt/ >operator>></a> - deserialize from stream</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">¶</a></h2> <ul> <li>Added in version 1.0.0.</li> <li>Overload for contiguous containers (1) added in version 2.0.3.</li> <li>Ignoring comments via <code>ignore_comments</code> added in version 3.9.0.</li> <li>Changed <a href=../../../features/assertions/ >runtime assertion</a> in case of <code>FILE*</code> null pointers to exception in version 3.12.0.</li> <li>Added <code>ignore_trailing_commas</code> in version 3.12.x.</li> </ul> <div class="admonition warning"> <p class=admonition-title>Deprecation</p> <p>Overload (2) replaces calls to <code>parse</code> with a pair of iterators as their first parameter which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like <code class=highlight><span class=n>parse</span><span class=p>({</span><span class=n>ptr</span><span class=p>,</span><span class=w> </span><span class=n>ptr</span><span class=o>+</span><span class=n>len</span><span class=p>},</span><span class=w> </span><span class=p>...);</span></code> with <code class=highlight><span class=n>parse</span><span class=p>(</span><span class=n>ptr</span><span class=p>,</span><span class=w> </span><span class=n>ptr</span><span class=o>+</span><span class=n>len</span><span class=p>,</span><span class=w> </span><span class=p>...);</span></code>.</p> <p>You should be warned by your compiler with a <code>-Wdeprecated-declarations</code> warning if you are using a deprecated function.</p> </div> <!-- 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 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=../accept/ >accept</a> - check if the input is valid <abbr title="JavaScript Object Notation">JSON</abbr></li> <li><a href=../sax_parse/ >sax_parse</a> - parse input using the <abbr title="Simple API for XML">SAX</abbr> interface</li> <li><a href=../../operator_gtgt/ >operator>></a> - deserialize from stream</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">¶</a></h2> <ul> <li>Added in version 1.0.0.</li> <li>Overload for contiguous containers (1) added in version 2.0.3.</li> <li>Ignoring comments via <code>ignore_comments</code> added in version 3.9.0.</li> <li>Changed <a href=../../../features/assertions/ >runtime assertion</a> in case of <code>FILE*</code> null pointers to exception in version 3.12.0.</li> <li>Added <code>ignore_trailing_commas</code> in version 3.12.x.</li> </ul> <div class="admonition warning"> <p class=admonition-title>Deprecation</p> <p>Overload (2) replaces calls to <code>parse</code> with a pair of iterators as their first parameter which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like <code class=highlight><span class=n>parse</span><span class=p>({</span><span class=n>ptr</span><span class=p>,</span><span class=w> </span><span class=n>ptr</span><span class=o>+</span><span class=n>len</span><span class=p>},</span><span class=w> </span><span class=p>...);</span></code> with <code class=highlight><span class=n>parse</span><span class=p>(</span><span class=n>ptr</span><span class=p>,</span><span class=w> </span><span class=n>ptr</span><span class=o>+</span><span class=n>len</span><span class=p>,</span><span class=w> </span><span class=p>...);</span></code>.</p> <p>You should be warned by your compiler with a <code>-Wdeprecated-declarations</code> warning if you are using a deprecated function.</p> </div> <!-- 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 Line truncated
|
||||
@@ -0,0 +1,624 @@
|
||||
# nlohmann::basic_json::parse
|
||||
|
||||
```
|
||||
// (1)
|
||||
template<typename InputType>
|
||||
static basic_json parse(InputType&& i,
|
||||
const parser_callback_t cb = nullptr,
|
||||
const bool allow_exceptions = true,
|
||||
const bool ignore_comments = false,
|
||||
const bool ignore_trailing_commas = false);
|
||||
|
||||
// (2)
|
||||
template<typename IteratorType>
|
||||
static basic_json parse(IteratorType first, IteratorType last,
|
||||
const parser_callback_t cb = nullptr,
|
||||
const bool allow_exceptions = true,
|
||||
const bool ignore_comments = false,
|
||||
const bool ignore_trailing_commas = false);
|
||||
```
|
||||
|
||||
1. Deserialize from a compatible input.
|
||||
|
||||
1. Deserialize from a pair of character iterators
|
||||
|
||||
The `value_type` of the iterator must be an integral type with size of 1, 2, or 4 bytes, which will be interpreted respectively as UTF-8, UTF-16, and UTF-32.
|
||||
|
||||
## Template parameters
|
||||
|
||||
`InputType` : A compatible input, for instance:
|
||||
|
||||
```
|
||||
- an `std::istream` object
|
||||
- a `FILE` pointer (throws if null)
|
||||
- a C-style array of characters
|
||||
- a pointer to a null-terminated string of single byte characters (throws if null)
|
||||
- a `std::string`
|
||||
- an object `obj` for which `begin(obj)` and `end(obj)` produces a valid pair of iterators.
|
||||
```
|
||||
|
||||
`IteratorType` : a compatible iterator type, for instance.
|
||||
|
||||
```
|
||||
- a pair of `std::string::iterator` or `std::vector<std::uint8_t>::iterator`
|
||||
- a pair of pointers such as `ptr` and `ptr + len`
|
||||
```
|
||||
|
||||
## Parameters
|
||||
|
||||
`i` (in) : Input to parse from.
|
||||
|
||||
`cb` (in) : a parser callback function of type [`parser_callback_t`](https://json.nlohmann.me/api/basic_json/parser_callback_t/index.md) which is used to control the deserialization by filtering unwanted values (optional)
|
||||
|
||||
`allow_exceptions` (in) : whether to throw exceptions in case of a parse error (optional, `true` by default)
|
||||
|
||||
`ignore_comments` (in) : whether comments should be ignored and treated like whitespace (`true`) or yield a parse error (`false`); (optional, `false` by default)
|
||||
|
||||
`ignore_trailing_commas` (in) : whether trailing commas in arrays or objects should be ignored and treated like whitespace (`true`) or yield a parse error (`false`); (optional, `false` by default)
|
||||
|
||||
`first` (in) : iterator to the start of a character range
|
||||
|
||||
`last` (in) : iterator to the end of a character range
|
||||
|
||||
## Return value
|
||||
|
||||
Deserialized JSON value; in case of a parse error and `allow_exceptions` set to `false`, the return value will be `value_t::discarded`. The latter can be checked with [`is_discarded`](https://json.nlohmann.me/api/basic_json/is_discarded/index.md).
|
||||
|
||||
## Exception safety
|
||||
|
||||
Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
|
||||
|
||||
## Exceptions
|
||||
|
||||
- Throws [`parse_error.101`](https://json.nlohmann.me/home/exceptions/#jsonexceptionparse_error101) in case of an unexpected token, or empty input like a null `FILE*` or `char*` pointer.
|
||||
|
||||
## Complexity
|
||||
|
||||
Linear in the length of the input. The parser is a predictive LL(1) parser. The complexity can be higher if the parser callback function `cb` or reading from (1) the input `i` or (2) the iterator range \[`first`, `last`\] has a super-linear complexity.
|
||||
|
||||
## Notes
|
||||
|
||||
A UTF-8 byte order mark is silently ignored.
|
||||
|
||||
Invalid Unicode escapes and unpaired surrogates in the input are reported as [`parse_error.101`](https://json.nlohmann.me/home/exceptions/#jsonexceptionparse_error101) with a detailed message.
|
||||
|
||||
## Examples
|
||||
|
||||
Parsing from a character array
|
||||
|
||||
The example below demonstrates the `parse()` function reading from an array.
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <iomanip>
|
||||
#include <nlohmann/json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
// a JSON text
|
||||
char text[] = R"(
|
||||
{
|
||||
"Image": {
|
||||
"Width": 800,
|
||||
"Height": 600,
|
||||
"Title": "View from 15th Floor",
|
||||
"Thumbnail": {
|
||||
"Url": "http://www.example.com/image/481989943",
|
||||
"Height": 125,
|
||||
"Width": 100
|
||||
},
|
||||
"Animated" : false,
|
||||
"IDs": [116, 943, 234, 38793]
|
||||
}
|
||||
}
|
||||
)";
|
||||
|
||||
// parse and serialize JSON
|
||||
json j_complete = json::parse(text);
|
||||
std::cout << std::setw(4) << j_complete << "\n\n";
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
{
|
||||
"Image": {
|
||||
"Animated": false,
|
||||
"Height": 600,
|
||||
"IDs": [
|
||||
116,
|
||||
943,
|
||||
234,
|
||||
38793
|
||||
],
|
||||
"Thumbnail": {
|
||||
"Height": 125,
|
||||
"Url": "http://www.example.com/image/481989943",
|
||||
"Width": 100
|
||||
},
|
||||
"Title": "View from 15th Floor",
|
||||
"Width": 800
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Parsing from a string
|
||||
|
||||
The example below demonstrates the `parse()` function with and without callback function.
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <iomanip>
|
||||
#include <nlohmann/json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
// a JSON text
|
||||
auto text = R"(
|
||||
{
|
||||
"Image": {
|
||||
"Width": 800,
|
||||
"Height": 600,
|
||||
"Title": "View from 15th Floor",
|
||||
"Thumbnail": {
|
||||
"Url": "http://www.example.com/image/481989943",
|
||||
"Height": 125,
|
||||
"Width": 100
|
||||
},
|
||||
"Animated" : false,
|
||||
"IDs": [116, 943, 234, 38793]
|
||||
}
|
||||
}
|
||||
)";
|
||||
|
||||
// parse and serialize JSON
|
||||
json j_complete = json::parse(text);
|
||||
std::cout << std::setw(4) << j_complete << "\n\n";
|
||||
|
||||
// define parser callback
|
||||
json::parser_callback_t cb = [](int depth, json::parse_event_t event, json & parsed)
|
||||
{
|
||||
// skip object elements with key "Thumbnail"
|
||||
if (event == json::parse_event_t::key and parsed == json("Thumbnail"))
|
||||
{
|
||||
return false;
|
||||
}
|
||||
else
|
||||
{
|
||||
return true;
|
||||
}
|
||||
};
|
||||
|
||||
// parse (with callback) and serialize JSON
|
||||
json j_filtered = json::parse(text, cb);
|
||||
std::cout << std::setw(4) << j_filtered << '\n';
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
{
|
||||
"Image": {
|
||||
"Animated": false,
|
||||
"Height": 600,
|
||||
"IDs": [
|
||||
116,
|
||||
943,
|
||||
234,
|
||||
38793
|
||||
],
|
||||
"Thumbnail": {
|
||||
"Height": 125,
|
||||
"Url": "http://www.example.com/image/481989943",
|
||||
"Width": 100
|
||||
},
|
||||
"Title": "View from 15th Floor",
|
||||
"Width": 800
|
||||
}
|
||||
}
|
||||
|
||||
{
|
||||
"Image": {
|
||||
"Animated": false,
|
||||
"Height": 600,
|
||||
"IDs": [
|
||||
116,
|
||||
943,
|
||||
234,
|
||||
38793
|
||||
],
|
||||
"Title": "View from 15th Floor",
|
||||
"Width": 800
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Parsing from an input stream
|
||||
|
||||
The example below demonstrates the `parse()` function with and without callback function.
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <iomanip>
|
||||
#include <sstream>
|
||||
#include <nlohmann/json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
// a JSON text
|
||||
auto text = R"(
|
||||
{
|
||||
"Image": {
|
||||
"Width": 800,
|
||||
"Height": 600,
|
||||
"Title": "View from 15th Floor",
|
||||
"Thumbnail": {
|
||||
"Url": "http://www.example.com/image/481989943",
|
||||
"Height": 125,
|
||||
"Width": 100
|
||||
},
|
||||
"Animated" : false,
|
||||
"IDs": [116, 943, 234, 38793]
|
||||
}
|
||||
}
|
||||
)";
|
||||
|
||||
// fill a stream with JSON text
|
||||
std::stringstream ss;
|
||||
ss << text;
|
||||
|
||||
// parse and serialize JSON
|
||||
json j_complete = json::parse(ss);
|
||||
std::cout << std::setw(4) << j_complete << "\n\n";
|
||||
|
||||
// define parser callback
|
||||
json::parser_callback_t cb = [](int depth, json::parse_event_t event, json & parsed)
|
||||
{
|
||||
// skip object elements with key "Thumbnail"
|
||||
if (event == json::parse_event_t::key and parsed == json("Thumbnail"))
|
||||
{
|
||||
return false;
|
||||
}
|
||||
else
|
||||
{
|
||||
return true;
|
||||
}
|
||||
};
|
||||
|
||||
// fill a stream with JSON text
|
||||
ss.clear();
|
||||
ss << text;
|
||||
|
||||
// parse (with callback) and serialize JSON
|
||||
json j_filtered = json::parse(ss, cb);
|
||||
std::cout << std::setw(4) << j_filtered << '\n';
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
{
|
||||
"Image": {
|
||||
"Animated": false,
|
||||
"Height": 600,
|
||||
"IDs": [
|
||||
116,
|
||||
943,
|
||||
234,
|
||||
38793
|
||||
],
|
||||
"Thumbnail": {
|
||||
"Height": 125,
|
||||
"Url": "http://www.example.com/image/481989943",
|
||||
"Width": 100
|
||||
},
|
||||
"Title": "View from 15th Floor",
|
||||
"Width": 800
|
||||
}
|
||||
}
|
||||
|
||||
{
|
||||
"Image": {
|
||||
"Animated": false,
|
||||
"Height": 600,
|
||||
"IDs": [
|
||||
116,
|
||||
943,
|
||||
234,
|
||||
38793
|
||||
],
|
||||
"Title": "View from 15th Floor",
|
||||
"Width": 800
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Parsing from a contiguous container
|
||||
|
||||
The example below demonstrates the `parse()` function reading from a contiguous container.
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <iomanip>
|
||||
#include <nlohmann/json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
// a JSON text given as std::vector
|
||||
std::vector<std::uint8_t> text = {'[', '1', ',', '2', ',', '3', ']', '\0'};
|
||||
|
||||
// parse and serialize JSON
|
||||
json j_complete = json::parse(text);
|
||||
std::cout << std::setw(4) << j_complete << "\n\n";
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
[
|
||||
1,
|
||||
2,
|
||||
3
|
||||
]
|
||||
```
|
||||
|
||||
Parsing from a non-null-terminated string
|
||||
|
||||
The example below demonstrates the `parse()` function reading from a string that is not null-terminated.
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <iomanip>
|
||||
#include <nlohmann/json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
// a JSON text given as string that is not null-terminated
|
||||
const char* ptr = "[1,2,3]another value";
|
||||
|
||||
// parse and serialize JSON
|
||||
json j_complete = json::parse(ptr, ptr + 7);
|
||||
std::cout << std::setw(4) << j_complete << "\n\n";
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
[
|
||||
1,
|
||||
2,
|
||||
3
|
||||
]
|
||||
```
|
||||
|
||||
Parsing from an iterator pair
|
||||
|
||||
The example below demonstrates the `parse()` function reading from an iterator pair.
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <iomanip>
|
||||
#include <nlohmann/json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
// a JSON text given an input with other values
|
||||
std::vector<std::uint8_t> input = {'[', '1', ',', '2', ',', '3', ']', 'o', 't', 'h', 'e', 'r'};
|
||||
|
||||
// parse and serialize JSON
|
||||
json j_complete = json::parse(input.begin(), input.begin() + 7);
|
||||
std::cout << std::setw(4) << j_complete << "\n\n";
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
[
|
||||
1,
|
||||
2,
|
||||
3
|
||||
]
|
||||
```
|
||||
|
||||
Effect of `allow_exceptions` parameter
|
||||
|
||||
The example below demonstrates the effect of the `allow_exceptions` parameter in the `parse()` function.
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <nlohmann/json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
// an invalid JSON text
|
||||
std::string text = R"(
|
||||
{
|
||||
"key": "value without closing quotes
|
||||
}
|
||||
)";
|
||||
|
||||
// parse with exceptions
|
||||
try
|
||||
{
|
||||
json j = json::parse(text);
|
||||
}
|
||||
catch (const json::parse_error& e)
|
||||
{
|
||||
std::cout << e.what() << std::endl;
|
||||
}
|
||||
|
||||
// parse without exceptions
|
||||
json j = json::parse(text, nullptr, false);
|
||||
|
||||
if (j.is_discarded())
|
||||
{
|
||||
std::cout << "the input is invalid JSON" << std::endl;
|
||||
}
|
||||
else
|
||||
{
|
||||
std::cout << "the input is valid JSON: " << j << std::endl;
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
[json.exception.parse_error.101] parse error at line 4, column 0: syntax error while parsing value - invalid string: control character U+000A (LF) must be escaped to \u000A or \n; last read: '"value without closing quotes<U+000A>'
|
||||
the input is invalid JSON
|
||||
```
|
||||
|
||||
Effect of `ignore_comments` parameter
|
||||
|
||||
The example below demonstrates the effect of the `ignore_comments` parameter in the `parse()` function.
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <nlohmann/json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
std::string s = R"(
|
||||
{
|
||||
// update in 2006: removed Pluto
|
||||
"planets": ["Mercury", "Venus", "Earth", "Mars",
|
||||
"Jupiter", "Uranus", "Neptune" /*, "Pluto" */]
|
||||
}
|
||||
)";
|
||||
|
||||
try
|
||||
{
|
||||
json j = json::parse(s);
|
||||
}
|
||||
catch (json::exception& e)
|
||||
{
|
||||
std::cout << e.what() << std::endl;
|
||||
}
|
||||
|
||||
json j = json::parse(s,
|
||||
/* callback */ nullptr,
|
||||
/* allow exceptions */ true,
|
||||
/* ignore_comments */ true);
|
||||
std::cout << j.dump(2) << '\n';
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
[json.exception.parse_error.101] parse error at line 3, column 9: syntax error while parsing object key - invalid literal; last read: '<U+000A> {<U+000A> /'; expected string literal
|
||||
{
|
||||
"planets": [
|
||||
"Mercury",
|
||||
"Venus",
|
||||
"Earth",
|
||||
"Mars",
|
||||
"Jupiter",
|
||||
"Uranus",
|
||||
"Neptune"
|
||||
]
|
||||
}
|
||||
```
|
||||
|
||||
Effect of `ignore_trailing_commas` parameter
|
||||
|
||||
The example below demonstrates the effect of the `ignore_trailing_commas` parameter in the `parse()` function.
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <nlohmann/json.hpp>
|
||||
|
||||
using json = nlohmann::json;
|
||||
|
||||
int main()
|
||||
{
|
||||
std::string s = R"(
|
||||
{
|
||||
"planets": [
|
||||
"Mercury",
|
||||
"Venus",
|
||||
"Earth",
|
||||
"Mars",
|
||||
"Jupiter",
|
||||
"Uranus",
|
||||
"Neptune",
|
||||
]
|
||||
}
|
||||
)";
|
||||
|
||||
try
|
||||
{
|
||||
json j = json::parse(s);
|
||||
}
|
||||
catch (json::exception& e)
|
||||
{
|
||||
std::cout << e.what() << std::endl;
|
||||
}
|
||||
|
||||
json j = json::parse(s,
|
||||
/* callback */ nullptr,
|
||||
/* allow exceptions */ true,
|
||||
/* ignore_comments */ false,
|
||||
/* ignore_trailing_commas */ true);
|
||||
std::cout << j.dump(2) << '\n';
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
[json.exception.parse_error.101] parse error at line 11, column 9: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
|
||||
{
|
||||
"planets": [
|
||||
"Mercury",
|
||||
"Venus",
|
||||
"Earth",
|
||||
"Mars",
|
||||
"Jupiter",
|
||||
"Uranus",
|
||||
"Neptune"
|
||||
]
|
||||
}
|
||||
```
|
||||
|
||||
## See also
|
||||
|
||||
- [accept](https://json.nlohmann.me/api/basic_json/accept/index.md) - check if the input is valid JSON
|
||||
- [sax_parse](https://json.nlohmann.me/api/basic_json/sax_parse/index.md) - parse input using the SAX interface
|
||||
- [operator>>](https://json.nlohmann.me/api/operator_gtgt/index.md) - deserialize from stream
|
||||
|
||||
## Version history
|
||||
|
||||
- Added in version 1.0.0.
|
||||
- Overload for contiguous containers (1) added in version 2.0.3.
|
||||
- Ignoring comments via `ignore_comments` added in version 3.9.0.
|
||||
- Changed [runtime assertion](https://json.nlohmann.me/features/assertions/index.md) in case of `FILE*` null pointers to exception in version 3.12.0.
|
||||
- Added `ignore_trailing_commas` in version 3.12.x.
|
||||
|
||||
Deprecation
|
||||
|
||||
Overload (2) replaces calls to `parse` with a pair of iterators as their first parameter which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like `parse({ptr, ptr+len}, ...);` with `parse(ptr, ptr+len, ...);`.
|
||||
|
||||
You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated function.
|
||||
Reference in new issue
Block a user