Niels Lohmann
8a0679558f
- Copying is disabled because of its cost, not because of two documents borrowing the same buffer; the unique_ptr follows from move-only. - Inputs: streams, FILE*, and wide characters (strings, arrays, pointers) are all supported and owned; point to parse_copy() for owned copies. - The error replay only runs for failing input, builds no values, and is skipped with allow_exceptions = false. - read() writes copied inputs into the previous owned copy. - Views can dangle like std::string_view, and why there is no shared/weak pointer design. - The 4 GiB limit (16-byte nodes, 16-byte scanner steps), streams being read to the end first, which macros apply, why materialize() has no source positions, and wording nits (accept() vs basic_json::accept(), is_binary, is_discarded, see-also lists, size table, "back into"). Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2.4 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 index builder (and discards the index), 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.
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 input
BasicJsonType::accept- the corresponding function ofbasic_json
Version history
- Added in version 3.13.0.