JSON for Modern C++ 3.10.4

◆ accept() [2/3]

template<template< typename U, typename V, typename... Args > class ObjectType = std::map, template< typename U, typename... Args > class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator, template< typename T, typename SFINAE=void > class JSONSerializer = adl_serializer, class BinaryType = std::vector<std::uint8_t>>
template<typename InputType >
static bool nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::accept ( InputType &&  i,
const bool  ignore_comments = false 

Unlike the parse(InputType&&, const parser_callback_t,const bool) function, this function neither throws an exception in case of invalid JSON input (i.e., a parse error) nor creates diagnostic information.

Template Parameters
InputTypeA compatible input, for instance
  • an std::istream object
  • a FILE pointer
  • a C-style array of characters
  • a pointer to a null-terminated string of single byte characters
  • an object obj for which begin(obj) and end(obj) produces a valid pair of iterators.
[in]iinput to read from
[in]ignore_commentswhether comments should be ignored and treated like whitespace (true) or yield a parse error (true); (optional, false by default)
Whether the input read from i is valid JSON.
Linear in the length of the input. The parser is a predictive LL(1) parser.
A UTF-8 byte order mark is silently ignored.
The example below demonstrates the accept() function reading from a string.
1#include <iostream>
2#include <iomanip>
3#include <nlohmann/json.hpp>
5using json = nlohmann::json;
7int main()
9 // a valid JSON text
10 auto valid_text = R"(
11 {
12 "numbers": [1, 2, 3]
13 }
14 )";
16 // an invalid JSON text
17 auto invalid_text = R"(
18 {
19 "strings": ["extra", "comma", ]
20 }
21 )";
23 std::cout << std::boolalpha
24 << json::accept(valid_text) << ' '
25 << json::accept(invalid_text) << '\n';
static bool accept(InputType &&i, const bool ignore_comments=false)
check if the input is valid JSON
Definition: json.hpp:24500
basic_json<> json
default JSON class
Definition: json.hpp:3472

Output (play with this example online):
true false
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/accept__string.cpp -o accept__string 

Definition at line 24500 of file json.hpp.