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</span> </a> <nav class="md-nav md-nav--secondary" aria-label="Table of contents"> <label class=md-nav__title for=__toc> <span class="md-nav__icon md-icon"></span> Table of contents </label> <ul class=md-nav__list data-md-component=toc data-md-scrollfix> <li class=md-nav__item> <a href=#overview class=md-nav__link> <span class=md-ellipsis> Overview </span> </a> </li> <li class=md-nav__item> <a href=#notes class=md-nav__link> <span class=md-ellipsis> Notes </span> </a> </li> <li class=md-nav__item> <a href=#summary class=md-nav__link> <span class=md-ellipsis> Summary </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../default_value/ class=md-nav__link> <span class=md-ellipsis> Access with default value: value </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../iterators/ class=md-nav__link> <span class=md-ellipsis> Iterators </span> </a> </li> <li class=md-nav__item> <a href=../../json_pointer/ class=md-nav__link> <span class=md-ellipsis> JSON Pointer </span> </a> </li> <li class=md-nav__item> <a href=../../json_patch/ class=md-nav__link> <span class=md-ellipsis> JSON Patch and Diff </span> </a> </li> <li class=md-nav__item> <a href=../../merge_patch/ class=md-nav__link> <span class=md-ellipsis> JSON Merge Patch </span> </a> </li> <li class=md-nav__item> <a href=../../namespace/ class=md-nav__link> <span class=md-ellipsis> nlohmann Namespace </span> </a> </li> <li class=md-nav__item> <a href=../../object_order/ class=md-nav__link> <span class=md-ellipsis> Object Order </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_2_12> <div class="md-nav__link md-nav__container"> <a href=../../parsing/ class="md-nav__link "> <span class=md-ellipsis> Parsing </span> </a> <label class="md-nav__link " for=__nav_2_12 id=__nav_2_12_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_2_12_label aria-expanded=false> <label class=md-nav__title for=__nav_2_12> <span class="md-nav__icon md-icon"></span> Parsing </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../parsing/json_lines/ class=md-nav__link> <span class=md-ellipsis> JSON Lines </span> </a> </li> <li class=md-nav__item> <a href=../../parsing/parse_exceptions/ class=md-nav__link> <span class=md-ellipsis> Parsing and Exceptions </span> </a> </li> <li class=md-nav__item> <a href=../../parsing/parser_callbacks/ class=md-nav__link> <span class=md-ellipsis> Parser Callbacks </span> </a> </li> <li class=md-nav__item> <a href=../../parsing/sax_interface/ class=md-nav__link> <span class=md-ellipsis> SAX Interface </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../assertions/ class=md-nav__link> <span class=md-ellipsis> Runtime Assertions </span> </a> </li> <li class=md-nav__item> <a href=../../enum_conversion/ class=md-nav__link> <span class=md-ellipsis> Specializing enum conversion </span> </a> </li> <li class=md-nav__item> <a href=../../macros/ class=md-nav__link> <span class=md-ellipsis> Supported Macros </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_2_16> <div class="md-nav__link md-nav__container"> <a href=../../types/ class="md-nav__link "> <span class=md-ellipsis> Types </span> </a> <label class="md-nav__link " for=__nav_2_16 id=__nav_2_16_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_2_16_label aria-expanded=false> <label class=md-nav__title for=__nav_2_16> <span class="md-nav__icon md-icon"></span> Types </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../types/number_handling/ class=md-nav__link> <span class=md-ellipsis> Number Handling </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_3> <div class="md-nav__link md-nav__container"> <a href=../../../integration/ class="md-nav__link "> <span class=md-ellipsis> Integration </span> </a> <label class="md-nav__link " for=__nav_3 id=__nav_3_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_3_label aria-expanded=false> <label class=md-nav__title for=__nav_3> <span class="md-nav__icon md-icon"></span> Integration </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../integration/migration_guide/ class=md-nav__link> <span class=md-ellipsis> Migration Guide </span> </a> </li> <li class=md-nav__item> <a href=../../../integration/cmake/ class=md-nav__link> <span class=md-ellipsis> CMake </span> </a> </li> <li class=md-nav__item> <a href=../../../integration/package_managers/ class=md-nav__link> <span class=md-ellipsis> Package Managers </span> </a> </li> <li class=md-nav__item> <a href=../../../integration/pkg-config/ class=md-nav__link> <span class=md-ellipsis> Pkg-config </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4> <label class=md-nav__link for=__nav_4 id=__nav_4_label tabindex=0> <span class=md-ellipsis> API Documentation </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_4_label aria-expanded=false> <label class=md-nav__title for=__nav_4> <span class="md-nav__icon md-icon"></span> API Documentation </label> <ul class=md-nav__list data-md-scrollfix> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_1> <div class="md-nav__link md-nav__container"> <a href=../../../api/basic_json/ class="md-nav__link "> <span class=md-ellipsis> basic_json </span> </a> <label class="md-nav__link " for=__nav_4_1 id=__nav_4_1_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_1_label aria-expanded=false> <label class=md-nav__title for=__nav_4_1> <span class="md-nav__icon md-icon"></span> basic_json </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../api/basic_json/basic_json/ class=md-nav__link> <span class=md-ellipsis> (Constructor) </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/~basic_json/ class=md-nav__link> <span class=md-ellipsis> (Destructor) </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/accept/ class=md-nav__link> <span class=md-ellipsis> accept </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/array/ class=md-nav__link> <span class=md-ellipsis> array </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/array_t/ class=md-nav__link> <span class=md-ellipsis> array_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/at/ class=md-nav__link> <span class=md-ellipsis> at </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/back/ class=md-nav__link> <span class=md-ellipsis> back </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/begin/ class=md-nav__link> <span class=md-ellipsis> begin </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/binary/ class=md-nav__link> <span class=md-ellipsis> binary </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/binary_t/ class=md-nav__link> <span class=md-ellipsis> binary_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/boolean_t/ class=md-nav__link> <span class=md-ellipsis> boolean_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/cbegin/ class=md-nav__link> <span class=md-ellipsis> cbegin </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/cbor_tag_handler_t/ class=md-nav__link> <span class=md-ellipsis> cbor_tag_handler_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/cend/ class=md-nav__link> <span class=md-ellipsis> cend </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/clear/ class=md-nav__link> <span class=md-ellipsis> clear </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/contains/ class=md-nav__link> <span class=md-ellipsis> contains </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/count/ class=md-nav__link> <span class=md-ellipsis> count </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/crbegin/ class=md-nav__link> <span class=md-ellipsis> crbegin </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/crend/ class=md-nav__link> <span class=md-ellipsis> crend </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/default_object_comparator_t/ class=md-nav__link> <span class=md-ellipsis> default_object_comparator_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/diff/ class=md-nav__link> <span class=md-ellipsis> diff </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/dump/ class=md-nav__link> <span class=md-ellipsis> dump </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/emplace/ class=md-nav__link> <span class=md-ellipsis> emplace </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/emplace_back/ class=md-nav__link> <span class=md-ellipsis> emplace_back </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/empty/ class=md-nav__link> <span class=md-ellipsis> empty </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/end/ class=md-nav__link> <span class=md-ellipsis> end </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/end_pos/ class=md-nav__link> <span class=md-ellipsis> end_pos </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/erase/ class=md-nav__link> <span class=md-ellipsis> erase </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/error_handler_t/ class=md-nav__link> <span class=md-ellipsis> error_handler_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/exception/ class=md-nav__link> <span class=md-ellipsis> exception </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/find/ class=md-nav__link> <span class=md-ellipsis> find </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/flatten/ class=md-nav__link> <span class=md-ellipsis> flatten </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/from_bjdata/ class=md-nav__link> <span class=md-ellipsis> from_bjdata </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/from_bson/ class=md-nav__link> <span class=md-ellipsis> from_bson </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/from_cbor/ class=md-nav__link> <span class=md-ellipsis> from_cbor </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/from_msgpack/ class=md-nav__link> <span class=md-ellipsis> from_msgpack </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/from_ubjson/ class=md-nav__link> <span class=md-ellipsis> from_ubjson </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/front/ class=md-nav__link> <span class=md-ellipsis> front </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/get/ class=md-nav__link> <span class=md-ellipsis> get </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/get_allocator/ class=md-nav__link> <span class=md-ellipsis> get_allocator </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/get_binary/ class=md-nav__link> <span class=md-ellipsis> get_binary </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/get_ptr/ class=md-nav__link> <span class=md-ellipsis> get_ptr </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/get_ref/ class=md-nav__link> <span class=md-ellipsis> get_ref </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/get_to/ class=md-nav__link> <span class=md-ellipsis> get_to </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/std_hash/ class=md-nav__link> <span class=md-ellipsis> std::hash&lt;basic_json&gt; </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/input_format_t/ class=md-nav__link> <span class=md-ellipsis> input_format_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/insert/ class=md-nav__link> <span class=md-ellipsis> insert </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/invalid_iterator/ class=md-nav__link> <span class=md-ellipsis> invalid_iterator </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_array/ class=md-nav__link> <span class=md-ellipsis> is_array </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_binary/ class=md-nav__link> <span class=md-ellipsis> is_binary </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_boolean/ class=md-nav__link> <span class=md-ellipsis> is_boolean </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_discarded/ class=md-nav__link> <span class=md-ellipsis> is_discarded </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_null/ class=md-nav__link> <span class=md-ellipsis> is_null </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_number/ class=md-nav__link> <span class=md-ellipsis> is_number </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_number_float/ class=md-nav__link> <span class=md-ellipsis> is_number_float </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_number_integer/ class=md-nav__link> <span class=md-ellipsis> is_number_integer </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_number_unsigned/ class=md-nav__link> <span class=md-ellipsis> is_number_unsigned </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_object/ class=md-nav__link> <span class=md-ellipsis> is_object </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_primitive/ class=md-nav__link> <span class=md-ellipsis> is_primitive </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_string/ class=md-nav__link> <span class=md-ellipsis> is_string </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/is_structured/ class=md-nav__link> <span class=md-ellipsis> is_structured </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/items/ class=md-nav__link> <span class=md-ellipsis> items </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/json_base_class_t/ class=md-nav__link> <span class=md-ellipsis> json_base_class_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/json_serializer/ class=md-nav__link> <span class=md-ellipsis> json_serializer </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/max_size/ class=md-nav__link> <span class=md-ellipsis> max_size </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/meta/ class=md-nav__link> <span class=md-ellipsis> meta </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/merge_patch/ class=md-nav__link> <span class=md-ellipsis> merge_patch </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/number_float_t/ class=md-nav__link> <span class=md-ellipsis> number_float_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/number_integer_t/ class=md-nav__link> <span class=md-ellipsis> number_integer_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/number_unsigned_t/ class=md-nav__link> <span class=md-ellipsis> number_unsigned_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/object/ class=md-nav__link> <span class=md-ellipsis> object </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/object_comparator_t/ class=md-nav__link> <span class=md-ellipsis> object_comparator_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/object_t/ class=md-nav__link> <span class=md-ellipsis> object_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator_ValueType/ class=md-nav__link> <span class=md-ellipsis> operator ValueType </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator_value_t/ class=md-nav__link> <span class=md-ellipsis> operator value_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator%5B%5D/ class=md-nav__link> <span class=md-ellipsis> operator[] </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator%3D/ class=md-nav__link> <span class=md-ellipsis> operator= </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator%2B%3D/ class=md-nav__link> <span class=md-ellipsis> operator+= </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator_eq/ class=md-nav__link> <span class=md-ellipsis> operator== </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator_ne/ class=md-nav__link> <span class=md-ellipsis> operator!= </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator_lt/ class=md-nav__link> <span class=md-ellipsis> operator< </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator_gt/ class=md-nav__link> <span class=md-ellipsis> operator> </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator_le/ class=md-nav__link> <span class=md-ellipsis> operator<= </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator_ge/ class=md-nav__link> <span class=md-ellipsis> operator>= </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/operator_spaceship/ class=md-nav__link> <span class=md-ellipsis> operator<=> </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/out_of_range/ class=md-nav__link> <span class=md-ellipsis> out_of_range </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/other_error/ class=md-nav__link> <span class=md-ellipsis> other_error </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/parse/ class=md-nav__link> <span class=md-ellipsis> parse </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/parse_error/ class=md-nav__link> <span class=md-ellipsis> parse_error </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/parse_event_t/ class=md-nav__link> <span class=md-ellipsis> parse_event_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/parser_callback_t/ class=md-nav__link> <span class=md-ellipsis> parser_callback_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/patch/ class=md-nav__link> <span class=md-ellipsis> patch </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/patch_inplace/ class=md-nav__link> <span class=md-ellipsis> patch_inplace </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/push_back/ class=md-nav__link> <span class=md-ellipsis> push_back </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/rbegin/ class=md-nav__link> <span class=md-ellipsis> rbegin </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/rend/ class=md-nav__link> <span class=md-ellipsis> rend </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/sax_parse/ class=md-nav__link> <span class=md-ellipsis> sax_parse </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/size/ class=md-nav__link> <span class=md-ellipsis> size </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/start_pos/ class=md-nav__link> <span class=md-ellipsis> start_pos </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/string_t/ class=md-nav__link> <span class=md-ellipsis> string_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/swap/ class=md-nav__link> <span class=md-ellipsis> swap </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/std_swap/ class=md-nav__link> <span class=md-ellipsis> std::swap&lt;basic_json&gt; </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/to_bjdata/ class=md-nav__link> <span class=md-ellipsis> to_bjdata </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/to_bson/ class=md-nav__link> <span class=md-ellipsis> to_bson </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/to_cbor/ class=md-nav__link> <span class=md-ellipsis> to_cbor </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/to_msgpack/ class=md-nav__link> <span class=md-ellipsis> to_msgpack </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/to_string/ class=md-nav__link> <span class=md-ellipsis> to_string </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/to_ubjson/ class=md-nav__link> <span class=md-ellipsis> to_ubjson </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/type/ class=md-nav__link> <span class=md-ellipsis> type </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/type_error/ class=md-nav__link> <span class=md-ellipsis> type_error </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/type_name/ class=md-nav__link> <span class=md-ellipsis> type_name </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/unflatten/ class=md-nav__link> <span class=md-ellipsis> unflatten </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/update/ class=md-nav__link> <span class=md-ellipsis> update </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/value/ class=md-nav__link> <span class=md-ellipsis> value </span> </a> </li> <li class=md-nav__item> <a href=../../../api/basic_json/value_t/ class=md-nav__link> <span class=md-ellipsis> value_t </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_2> <div class="md-nav__link md-nav__container"> <a href=../../../api/byte_container_with_subtype/ class="md-nav__link "> <span class=md-ellipsis> byte_container_with_subtype </span> </a> <label class="md-nav__link " for=__nav_4_2 id=__nav_4_2_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_2_label aria-expanded=false> <label class=md-nav__title for=__nav_4_2> <span class="md-nav__icon md-icon"></span> byte_container_with_subtype </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../api/byte_container_with_subtype/byte_container_with_subtype/ class=md-nav__link> <span class=md-ellipsis> (constructor) </span> </a> </li> <li class=md-nav__item> <a href=../../../api/byte_container_with_subtype/clear_subtype/ class=md-nav__link> <span class=md-ellipsis> clear_subtype </span> </a> </li> <li class=md-nav__item> <a href=../../../api/byte_container_with_subtype/has_subtype/ class=md-nav__link> <span class=md-ellipsis> has_subtype </span> </a> </li> <li class=md-nav__item> <a href=../../../api/byte_container_with_subtype/set_subtype/ class=md-nav__link> <span class=md-ellipsis> set_subtype </span> </a> </li> <li class=md-nav__item> <a href=../../../api/byte_container_with_subtype/subtype/ class=md-nav__link> <span class=md-ellipsis> subtype </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_3> <div class="md-nav__link md-nav__container"> <a href=../../../api/adl_serializer/ class="md-nav__link "> <span class=md-ellipsis> adl_serializer </span> </a> <label class="md-nav__link " for=__nav_4_3 id=__nav_4_3_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_3_label aria-expanded=false> <label class=md-nav__title for=__nav_4_3> <span class="md-nav__icon md-icon"></span> adl_serializer </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../api/adl_serializer/from_json/ class=md-nav__link> <span class=md-ellipsis> from_json </span> </a> </li> <li class=md-nav__item> <a href=../../../api/adl_serializer/to_json/ class=md-nav__link> <span class=md-ellipsis> to_json </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../../api/json/ class=md-nav__link> <span class=md-ellipsis> json </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_5> <div class="md-nav__link md-nav__container"> <a href=../../../api/json_pointer/ class="md-nav__link "> <span class=md-ellipsis> json_pointer </span> </a> <label class="md-nav__link " for=__nav_4_5 id=__nav_4_5_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_5_label aria-expanded=false> <label class=md-nav__title for=__nav_4_5> <span class="md-nav__icon md-icon"></span> json_pointer </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../api/json_pointer/json_pointer/ class=md-nav__link> <span class=md-ellipsis> (Constructor) </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/back/ class=md-nav__link> <span class=md-ellipsis> back </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/empty/ class=md-nav__link> <span class=md-ellipsis> empty </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/operator_string_t/ class=md-nav__link> <span class=md-ellipsis> operator string_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/operator_eq/ class=md-nav__link> <span class=md-ellipsis> operator== </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/operator_ne/ class=md-nav__link> <span class=md-ellipsis> operator!= </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/operator_slash/ class=md-nav__link> <span class=md-ellipsis> operator/ </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/operator_slasheq/ class=md-nav__link> <span class=md-ellipsis> operator/= </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/parent_pointer/ class=md-nav__link> <span class=md-ellipsis> parent_pointer </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/pop_back/ class=md-nav__link> <span class=md-ellipsis> pop_back </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/push_back/ class=md-nav__link> <span class=md-ellipsis> push_back </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/string_t/ class=md-nav__link> <span class=md-ellipsis> string_t </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_pointer/to_string/ class=md-nav__link> <span class=md-ellipsis> to_string </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_6> <div class="md-nav__link md-nav__container"> <a href=../../../api/json_sax/ class="md-nav__link "> <span class=md-ellipsis> json_sax </span> </a> <label class="md-nav__link " for=__nav_4_6 id=__nav_4_6_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_6_label aria-expanded=false> <label class=md-nav__title for=__nav_4_6> <span class="md-nav__icon md-icon"></span> json_sax </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../api/json_sax/binary/ class=md-nav__link> <span class=md-ellipsis> binary </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/boolean/ class=md-nav__link> <span class=md-ellipsis> boolean </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/end_array/ class=md-nav__link> <span class=md-ellipsis> end_array </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/end_object/ class=md-nav__link> <span class=md-ellipsis> end_object </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/key/ class=md-nav__link> <span class=md-ellipsis> key </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/null/ class=md-nav__link> <span class=md-ellipsis> null </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/number_float/ class=md-nav__link> <span class=md-ellipsis> number_float </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/number_integer/ class=md-nav__link> <span class=md-ellipsis> number_integer </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/number_unsigned/ class=md-nav__link> <span class=md-ellipsis> number_unsigned </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/parse_error/ class=md-nav__link> <span class=md-ellipsis> parse_error </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/start_array/ class=md-nav__link> <span class=md-ellipsis> start_array </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/start_object/ class=md-nav__link> <span class=md-ellipsis> start_object </span> </a> </li> <li class=md-nav__item> <a href=../../../api/json_sax/string/ class=md-nav__link> <span class=md-ellipsis> string </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../../api/operator_ltlt/ class=md-nav__link> <span class=md-ellipsis> operator<<(basic_json), operator<<(json_pointer) </span> </a> </li> <li class=md-nav__item> <a href=../../../api/operator_gtgt/ class=md-nav__link> <span class=md-ellipsis> operator>>(basic_json) </span> </a> </li> <li class=md-nav__item> <a href=../../../api/operator_literal_json/ class=md-nav__link> <span class=md-ellipsis> operator""_json </span> </a> </li> <li class=md-nav__item> <a href=../../../api/operator_literal_json_pointer/ class=md-nav__link> <span class=md-ellipsis> operator""_json_pointer </span> </a> </li> <li class=md-nav__item> <a href=../../../api/ordered_json/ class=md-nav__link> <span class=md-ellipsis> ordered_json </span> </a> </li> <li class=md-nav__item> <a href=../../../api/ordered_map/ class=md-nav__link> <span class=md-ellipsis> ordered_map </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_13> <div class="md-nav__link md-nav__container"> <a href=../../../api/macros/ class="md-nav__link "> <span class=md-ellipsis> macros </span> </a> <label class="md-nav__link " for=__nav_4_13 id=__nav_4_13_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_13_label aria-expanded=false> <label class=md-nav__title for=__nav_4_13> <span class="md-nav__icon md-icon"></span> macros </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../api/macros/json_assert/ class=md-nav__link> <span class=md-ellipsis> JSON_ASSERT </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_throw_user/ class=md-nav__link> <span class=md-ellipsis> JSON_CATCH_USER, JSON_THROW_USER, JSON_TRY_USER </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_diagnostics/ class=md-nav__link> <span class=md-ellipsis> JSON_DIAGNOSTICS </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_diagnostic_positions/ class=md-nav__link> <span class=md-ellipsis> JSON_DIAGNOSTIC_POSITIONS </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_disable_enum_serialization/ class=md-nav__link> <span class=md-ellipsis> JSON_DISABLE_ENUM_SERIALIZATION </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_has_cpp_11/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_CPP_11, JSON_HAS_CPP_14, JSON_HAS_CPP_17, JSON_HAS_CPP_20 </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_has_filesystem/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_EXPERIMENTAL_FILESYSTEM, JSON_HAS_FILESYSTEM </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_has_ranges/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_RANGES </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_has_static_rtti/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_STATIC_RTTI </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_has_three_way_comparison/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_THREE_WAY_COMPARISON </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_noexception/ class=md-nav__link> <span class=md-ellipsis> JSON_NOEXCEPTION </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_no_io/ class=md-nav__link> <span class=md-ellipsis> JSON_NO_IO </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_skip_library_version_check/ class=md-nav__link> <span class=md-ellipsis> JSON_SKIP_LIBRARY_VERSION_CHECK </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_skip_unsupported_compiler_check/ class=md-nav__link> <span class=md-ellipsis> JSON_SKIP_UNSUPPORTED_COMPILER_CHECK </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_use_global_udls/ class=md-nav__link> <span class=md-ellipsis> JSON_USE_GLOBAL_UDLS </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_use_implicit_conversions/ class=md-nav__link> <span class=md-ellipsis> JSON_USE_IMPLICIT_CONVERSIONS </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/json_use_legacy_discarded_value_comparison/ class=md-nav__link> <span class=md-ellipsis> JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/nlohmann_define_derived_type/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/nlohmann_define_type_intrusive/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_DEFINE_TYPE_INTRUSIVE, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/nlohmann_define_type_non_intrusive/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/nlohmann_json_namespace/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_JSON_NAMESPACE </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/nlohmann_json_namespace_begin/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/nlohmann_json_namespace_no_version/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_JSON_NAMESPACE_NO_VERSION </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/nlohmann_json_serialize_enum/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_JSON_SERIALIZE_ENUM </span> </a> </li> <li class=md-nav__item> <a href=../../../api/macros/nlohmann_json_version_major/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_JSON_VERSION_MAJOR, NLOHMANN_JSON_VERSION_MINOR, NLOHMANN_JSON_VERSION_PATCH </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_5> <div class="md-nav__link md-nav__container"> <a href=../../../community/ class="md-nav__link "> <span class=md-ellipsis> Community </span> </a> <label class="md-nav__link " for=__nav_5 id=__nav_5_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_5_label aria-expanded=false> <label class=md-nav__title for=__nav_5> <span class="md-nav__icon md-icon"></span> Community </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../../community/code_of_conduct/ class=md-nav__link> <span class=md-ellipsis> Code of Conduct </span> </a> </li> <li class=md-nav__item> <a href=../../../community/contribution_guidelines/ class=md-nav__link> <span class=md-ellipsis> Contribution Guidelines </span> </a> </li> <li class=md-nav__item> <a href=../../../community/quality_assurance/ class=md-nav__link> <span class=md-ellipsis> Quality assurance </span> </a> </li> <li class=md-nav__item> <a href=../../../community/governance/ class=md-nav__link> <span class=md-ellipsis> Governance </span> </a> </li> <li class=md-nav__item> <a href=../../../community/security_policy/ class=md-nav__link> <span class=md-ellipsis> Security Policy </span> </a> </li> </ul> </nav> </li> </ul> </nav> </div> </div> </div> <div class="md-sidebar md-sidebar--secondary" data-md-component=sidebar data-md-type=toc> <div class=md-sidebar__scrollwrap> <div class=md-sidebar__inner> <nav class="md-nav md-nav--secondary" aria-label="Table of contents"> <label class=md-nav__title for=__toc> <span class="md-nav__icon md-icon"></span> Table of contents </label> <ul class=md-nav__list data-md-component=toc data-md-scrollfix> <li class=md-nav__item> <a href=#overview class=md-nav__link> <span class=md-ellipsis> Overview </span> </a> </li> <li class=md-nav__item> <a href=#notes class=md-nav__link> <span class=md-ellipsis> Notes </span> </a> </li> <li class=md-nav__item> <a href=#summary class=md-nav__link> <span class=md-ellipsis> Summary </span> </a> </li> </ul> </nav> </div> </div> </div> <div class=md-content data-md-component=content> <article class="md-content__inner md-typeset"> <a href="https://github.com/nlohmann/json/edit/develop/docs/mkdocs/docs/features/element_access/checked_access.md" title="Edit this page" class="md-content__button md-icon"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M10 20H6V4h7v5h5v3.1l2-2V8l-6-6H6c-1.1 0-2 .9-2 2v16c0 1.1.9 2 2 2h4zm10.2-7c.1 0 .3.1.4.2l1.3 1.3c.2.2.2.6 0 .8l-1 1-2.1-2.1 1-1c.1-.1.2-.2.4-.2m0 3.9L14.1 23H12v-2.1l6.1-6.1z"/></svg> </a> <a href="https://github.com/nlohmann/json/raw/develop/docs/mkdocs/docs/features/element_access/checked_access.md" title="View source of this page" class="md-content__button md-icon"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M17 18c.56 0 1 .44 1 1s-.44 1-1 1-1-.44-1-1 .44-1 1-1m0-3c-2.73 0-5.06 1.66-6 4 .94 2.34 3.27 4 6 4s5.06-1.66 6-4c-.94-2.34-3.27-4-6-4m0 6.5a2.5 2.5 0 0 1-2.5-2.5 2.5 2.5 0 0 1 2.5-2.5 2.5 2.5 0 0 1 2.5 2.5 2.5 2.5 0 0 1-2.5 2.5M9.27 20H6V4h7v5h5v4.07c.7.08 1.36.25 2 .49V8l-6-6H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h4.5a8.2 8.2 0 0 1-1.23-2"/></svg> </a> <h1 id=checked-access-at>Checked access: at<a class=headerlink href=#checked-access-at title="Permanent link">&para;</a></h1> <h2 id=overview>Overview<a class=headerlink href=#overview title="Permanent link">&para;</a></h2> <p>The <a href=../../../api/basic_json/at/ ><code>at</code></a> member function performs checked access; that is, it returns a reference to the desired value if it exists and throws a <a href=../../../home/exceptions/#out-of-range><code>basic_json::out_of_range</code> exception</a> otherwise.</p> <details class=example> <summary>Read access</summary> <p>Consider the following <abbr title="JavaScript Object Notation">JSON</abbr> value:</p> <div class=highlight><pre><span></span><code><span class=p>{</span>
<span class=w>    </span><span class=nt>&quot;name&quot;</span><span class=p>:</span><span class=w> </span><span class=s2>&quot;Mary Smith&quot;</span><span class=p>,</span>
<span class=w>    </span><span class=nt>&quot;age&quot;</span><span class=p>:</span><span class=w> </span><span class=mi>42</span><span class=p>,</span>
<span class=w>    </span><span class=nt>&quot;hobbies&quot;</span><span class=p>:</span><span class=w> </span><span class=p>[</span><span class=s2>&quot;hiking&quot;</span><span class=p>,</span><span class=w> </span><span class=s2>&quot;reading&quot;</span><span class=p>]</span>
<span class=p>}</span>
</code></pre></div> <p>Assume the value is parsed to a <code>json</code> variable <code>j</code>.</p> <table> <thead> <tr> <th>expression</th> <th>value</th> </tr> </thead> <tbody> <tr> <td><code class=highlight><span class=n>j</span></code></td> <td><code class=highlight><span class=p>{</span><span class=nt>&quot;name&quot;</span><span class=p>:</span><span class=w> </span><span class=s2>&quot;Mary Smith&quot;</span><span class=p>,</span><span class=w> </span><span class=nt>&quot;age&quot;</span><span class=p>:</span><span class=w> </span><span class=mi>42</span><span class=p>,</span><span class=w> </span><span class=nt>&quot;hobbies&quot;</span><span class=p>:</span><span class=w> </span><span class=p>[</span><span class=s2>&quot;hiking&quot;</span><span class=p>,</span><span class=w> </span><span class=s2>&quot;reading&quot;</span><span class=p>]}</span></code></td> </tr> <tr> <td><code class=highlight><span class=n>j</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=s>&quot;name&quot;</span><span class=p>)</span></code></td> <td><code class=highlight><span class=s2>&quot;Mary Smith&quot;</span></code></td> </tr> <tr> <td><code class=highlight><span class=n>j</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=s>&quot;age&quot;</span><span class=p>)</span></code></td> <td><code class=highlight><span class=mi>42</span></code></td> </tr> <tr> <td><code class=highlight><span class=n>j</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=s>&quot;hobbies&quot;</span><span class=p>)</span></code></td> <td><code class=highlight><span class=p>[</span><span class=s2>&quot;hiking&quot;</span><span class=p>,</span><span class=w> </span><span class=s2>&quot;reading&quot;</span><span class=p>]</span></code></td> </tr> <tr> <td><code class=highlight><span class=n>j</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=s>&quot;hobbies&quot;</span><span class=p>).</span><span class=n>at</span><span class=p>(</span><span class=mi>0</span><span class=p>)</span></code></td> <td><code class=highlight><span class=s2>&quot;hiking&quot;</span></code></td> </tr> <tr> <td><code class=highlight><span class=n>j</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=s>&quot;hobbies&quot;</span><span class=p>).</span><span class=n>at</span><span class=p>(</span><span class=mi>1</span><span class=p>)</span></code></td> <td><code class=highlight><span class=s2>&quot;reading&quot;</span></code></td> </tr> </tbody> </table> </details> <p>The return value is a reference, so it can be modified by the original value.</p> <details class=example> <summary>Write access</summary> <div class=highlight><pre><span></span><code><span class=n>j</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=s>&quot;name&quot;</span><span class=p>)</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>&quot;John Smith&quot;</span><span class=p>;</span>
</code></pre></div> <p>This code produces the following <abbr title="JavaScript Object Notation">JSON</abbr> value:</p> <div class=highlight><pre><span></span><code><span class=p>{</span>
<span class=w>    </span><span class=nt>&quot;name&quot;</span><span class=p>:</span><span class=w> </span><span class=s2>&quot;John Smith&quot;</span><span class=p>,</span>
<span class=w>    </span><span class=nt>&quot;age&quot;</span><span class=p>:</span><span class=w> </span><span class=mi>42</span><span class=p>,</span>
<span class=w>    </span><span class=nt>&quot;hobbies&quot;</span><span class=p>:</span><span class=w> </span><span class=p>[</span><span class=s2>&quot;hiking&quot;</span><span class=p>,</span><span class=w> </span><span class=s2>&quot;reading&quot;</span><span class=p>]</span>
<span class=p>}</span>
</code></pre></div> </details> <p>When accessing an invalid index (i.e., an index greater than or equal to the array size) or the passed object key is non-existing, an exception is thrown.</p> <details class=example> <summary>Accessing via invalid index or missing key</summary> <div class=highlight><pre><span></span><code><span class=n>j</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=s>&quot;hobbies&quot;</span><span class=p>).</span><span class=n>at</span><span class=p>(</span><span class=mi>3</span><span class=p>)</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>&quot;cooking&quot;</span><span class=p>;</span>
</code></pre></div> <p>This code produces the following exception:</p> <div class=highlight><pre><span></span><code>[json.exception.out_of_range.401] array index 3 is out of range
</code></pre></div> <p>When you <a href=../../../home/exceptions/#extended-diagnostic-messages>extended diagnostic messages</a> are enabled by defining <a href=../../../api/macros/json_diagnostics/ ><code>JSON_DIAGNOSTICS</code></a>, the exception further gives information where the key or index is missing or out of range.</p> <div class=highlight><pre><span></span><code>[json.exception.out_of_range.401] (/hobbies) array index 3 is out of range
</code></pre></div> </details> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition failure"> <p class=admonition-title>Exceptions</p> <ul> <li><a href=../../../api/basic_json/at/ ><code>at</code></a> can only be used with objects (with a string argument) or with arrays (with a numeric argument). For other types, a <a href=../../../home/exceptions/#jsonexceptiontype_error304><code>basic_json::type_error</code></a> is thrown.</li> <li><a href=../../../home/exceptions/#out-of-range><code>basic_json::out_of_range</code> exception</a> exceptions are thrown if the provided key is not found in an object or the provided index is invalid.</li> </ul> </div> <h2 id=summary>Summary<a class=headerlink href=#summary title="Permanent link">&para;</a></h2> <table> <thead> <tr> <th>scenario</th> <th>non-const value</th> <th>const value</th> </tr> </thead> <tbody> <tr> <td>access to existing object key</td> <td>reference to existing value is returned</td> <td>const reference to existing value is returned</td> </tr> <tr> <td>access to valid array index</td> <td>reference to existing value is returned</td> <td>const reference to existing value is returned</td> </tr> <tr> <td>access to non-existing object key</td> <td><code>basic_json::out_of_range</code> exception is thrown</td> <td><code>basic_json::out_of_range</code> exception is thrown</td> </tr> <tr> <td>access to invalid array index</td> <td><code>basic_json::out_of_range</code> exception is thrown</td> <td><code>basic_json::out_of_range</code> exception is thrown</td> </tr> </tbody> </table> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date">January 20, 2025</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2025 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 496 512"><!-- Font Awesome Free 6.7.2 by @fontawesome - 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