allocator_type array array_t at at at at at at back back basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json begin begin boolean_t cbegin cend clear const_iterator const_pointer const_reference const_reverse_iterator count crbegin crend detail::external_constructor diff difference_type dump emplace emplace_back empty end end erase erase erase erase find find flatten from_cbor from_msgpack front front get get get get get get_allocator get_ptr get_ptr get_ref get_ref insert insert insert insert insert is_array is_boolean is_discarded is_null is_number is_number_float is_number_integer is_number_unsigned is_object is_primitive is_string is_structured iterator iterator_wrapper iterator_wrapper json_serializer max_size meta number_float_t number_integer_t number_unsigned_t object object_t operator value_t operator ValueType operator!= operator!= operator!= operator+= operator+= operator+= operator+= operator< operator<< operator<< operator<= operator= operator== operator== operator== operator> operator>= operator>> operator>> operator[] operator[] operator[] operator[] operator[] operator[] operator[] operator[] operator[] operator[] parse parse parse parse parse parse parse_event_t parser_callback_t patch pointer push_back push_back push_back push_back rbegin rbegin reference rend rend reverse_iterator size size_type string_t swap swap swap swap to_cbor to_msgpack type type_name unflatten value value value value value_t value_type ~basic_json

at() [5/6] 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> reference nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer >::at ( const json_pointer &  ptr ) inline Returns a reference to the element at with specified JSON pointer ptr, with bounds checking. Parameters [in] ptr JSON pointer to the desired element Returns reference to the element pointed to by ptr Complexity Constant. Exceptions std::out_of_range if the JSON pointer can not be resolved std::domain_error if an array index begins with '0' std::invalid_argument if an array index was not a number Example The behavior is shown in the example. #include <json.hpp> using json = nlohmann::json; int main() { // create a JSON value json j = { {"number", 1}, {"string", "foo"}, {"array", {1, 2}} }; // read-only access // output element with JSON pointer "/number" std::cout << j.at("/number"_json_pointer) << '\n'; // output element with JSON pointer "/string" std::cout << j.at("/string"_json_pointer) << '\n'; // output element with JSON pointer "/array" std::cout << j.at("/array"_json_pointer) << '\n'; // output element with JSON pointer "/array/1" std::cout << j.at("/array/1"_json_pointer) << '\n'; // writing access // change the string j.at("/string"_json_pointer) = "bar"; // output the changed string std::cout << j["string"] << '\n'; // change an array element j.at("/array/1"_json_pointer) = 21; // output the changed array std::cout << j["array"] << '\n'; } Output (play with this example online): 1 "foo" [1,2] 2 "bar" [1,21] The example code above can be translated with g++ -std=c++11 -Isrc doc/examples/at_json_pointer.cpp -o at_json_pointer Since version 2.0.0 Definition at line 12034 of file json.hpp.