Niels Lohmann
6a852ab96d
* Split the json_view feature page into sub-pages
The single features/json_view.md page grew to ~600 lines covering eight
topics. Split it into features/json_view/ with an overview page and
pages for ownership and lifetime, differences from basic_json, reading
values, generic code, editing, and images.
The new differences page collects what was spread over several sections
("What is the same", "What is different", "Duplicate keys", and notes in
the conversion and serialization sections) under one summary table, and
adds the parts of the basic_json interface a view does not have. The
other pages now link to it instead of restating the rules.
Internal links across the documentation point to the new pages.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Docs: fix stale comments and trim repeated text in json_view pages
- fig-jsonview.js/.css: point the header comments at the new pages
- reading.md: views' strings are valid as long as the document (and a
borrowed source text), as lifetime.md says
- reading.md, generic_code.md: link to differences.md instead of
restating the member-order and repeated-key rules
- differences.md: drop the third mention of ordering comparisons, name
rbegin()/rend() in the iterator row
- exceptions.md: link editable documents to editing.md
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
1.2 KiB
1.2 KiB
nlohmann::basic_json_document::is_discarded
bool is_discarded() const noexcept;
Returns whether the document holds no value, either because it was default-constructed or because the last call to
parse(), parse_copy(), or read() failed with allow_exceptions set to
#!cpp false.
Return value
#!cpp true if the document is discarded, #!cpp false otherwise.
Exception safety
No-throw guarantee: this function never throws exceptions.
Complexity
Constant.
Notes
When the document is discarded, root() returns a discarded view (its
is_discarded() is also #!cpp true).
Examples
??? example
```cpp
--8<-- "examples/basic_json_document__is_discarded.cpp"
```
Output:
```json
--8<-- "examples/basic_json_document__is_discarded.output"
```
See also
parse- deserialize from a compatible inputbasic_json_view::is_discarded- return whether a view is invalid- Zero-copy JSON views - how a discarded document arises
Version history
- Added in version 3.13.0.