Niels Lohmann
83322fe0ad
Address review of #5970: - build() takes validate_only as an argument; the validate_only members of document_data and basic_json_document are removed, so neither grows - the internal read path takes an on_error mode (discard, raise, validate) instead of allow_exceptions; accept() calls it with on_error::validate - build_with() has no default for Store - drop the unneeded static_casts in push_node() - name the NulIsEnd argument so astyle keeps build<...> intact - explain in the docs and code why comments/trailing commas keep the index Signed-off-by: Niels Lohmann <mail@nlohmann.me>
3.0 KiB
nlohmann::basic_json_document::accept
template<typename InputType>
static bool accept(InputType&& input,
const bool ignore_comments = false,
const bool ignore_trailing_commas = false);
Checks whether the input is valid JSON, accepting and rejecting exactly what
BasicJsonType::accept() does, with the same options. Unlike parse(), this
function never throws an exception for invalid input, and the returned #!cpp bool is the only result — no document
is returned.
The result is the same as that of BasicJsonType::accept() by design; the difference is how the check is made. This
function runs the document's builder, which checks the text as parse() does, while
BasicJsonType::accept() runs the SAX parser with a handler that ignores every event. Use this one if you go on to
parse the same input with parse() anyway, so that both use the same code; either is fine for a plain
yes/no answer.
When both ignore_comments and ignore_trailing_commas are #!cpp false (the default), the builder writes no index.
With either option set, it builds the index as parse() does and discards it: the result is the same, only
the time differs. (Neither option needs the index; the variant that skips it exists only for the default options to
keep the code size down.)
Template parameters
InputType- A compatible input; see
parse.
Parameters
input(in)- Input to check.
ignore_comments(in)- whether comments should be ignored and treated like whitespace (
#!cpp true) or yield a parse error (#!cpp false); (optional,#!cpp falseby default) ignore_trailing_commas(in)- whether trailing commas in arrays or objects should be ignored and treated like whitespace (
#!cpp true) or yield a parse error (#!cpp false); (optional,#!cpp falseby default)
Return value
Whether the input is valid JSON.
Exception safety
Strong guarantee: this function itself never throws for an invalid input; it can only throw what allocating the input's own copy (for inputs that are always read into a buffer) throws.
Complexity
Linear in the length of the input.
Notes
An integer argument that is not a #!cpp bool where the flags are expected, such as #!cpp accept(ptr, len), does not
compile; see parse.
Examples
??? example
```cpp
--8<-- "examples/basic_json_document__accept.cpp"
```
Output:
```json
--8<-- "examples/basic_json_document__accept.output"
```
See also
parse- deserialize from a compatible inputBasicJsonType::accept- the corresponding function ofbasic_json- Zero-copy JSON views - how parsing a document differs from, and matches, basic_json::parse
Version history
- Added in version 3.13.0.