accept accept accept 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 basic_json begin begin binary binary binary binary binary_t boolean_t cbegin cbor_tag_handler_t cend clear const_iterator const_pointer const_reference const_reverse_iterator contains contains count crbegin crend detail::external_constructor diff difference_type dump emplace emplace_back empty end end erase erase erase erase error_handler_t exception find find flatten from_bson from_bson from_bson from_bson from_cbor from_cbor from_cbor from_cbor from_msgpack from_msgpack from_msgpack from_msgpack from_ubjson from_ubjson from_ubjson from_ubjson front front get get get get get get get_allocator get_binary get_binary get_ptr get_ptr get_ref get_ref get_to get_to get_to initializer_list_t input_format_t insert insert insert insert insert insert insert_iterator invalid_iterator is_array is_binary 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 items items iterator iterator_wrapper iterator_wrapper json_pointer json_sax_t json_serializer max_size merge_patch meta number_float_t number_integer_t number_unsigned_t object object_comparator_t 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[] operator[] operator[] operator[] operator[] operator[] operator[] other_error out_of_range parse parse parse parse_error parse_event_t parser_callback_t patch pointer push_back push_back push_back push_back rbegin rbegin reference rend rend reverse_iterator sax_parse sax_parse sax_parse size size_type string_t swap swap swap swap swap swap swap to_bson to_bson to_bson to_cbor to_cbor to_cbor to_msgpack to_msgpack to_msgpack to_ubjson to_ubjson to_ubjson type type_error type_name unflatten update update value value value value value_t value_type ~basic_json

contains() [1/2] bool nlohmann::basic_json::contains ( const json_pointer &  ptr ) const inline Check whether the given JSON pointer ptr can be resolved in the current JSON value. Note This method can be executed on any JSON value type. Parameters [in] ptr JSON pointer to check its existence. Returns true if the JSON pointer can be resolved to a stored value, false otherwise. Postcondition If j.contains(ptr) returns true, it is safe to call j[ptr]. Exceptions parse_error.106 if an array index begins with '0' parse_error.109 if an array index was not a number Complexity Logarithmic in the size of the JSON object. Example The following code shows an example for contains(). #include <iostream> #include <nlohmann/json.hpp> using json = nlohmann::json; int main() { // create a JSON value json j = { {"number", 1}, {"string", "foo"}, {"array", {1, 2}} }; std::cout << std::boolalpha << j.contains("/number"_json_pointer) << '\n' << j.contains("/string"_json_pointer) << '\n' << j.contains("/array"_json_pointer) << '\n' << j.contains("/array/1"_json_pointer) << '\n' << j.contains("/array/-"_json_pointer) << '\n' << j.contains("/array/4"_json_pointer) << '\n' << j.contains("/baz"_json_pointer) << std::endl; try { // try to use an array index with leading '0' j.contains("/array/01"_json_pointer); } catch (json::parse_error& e) { std::cout << e.what() << '\n'; } try { // try to use an array index that is not a number j.contains("/array/one"_json_pointer); } catch (json::parse_error& e) { std::cout << e.what() << '\n'; } } Output (play with this example online): true true true true false false false The example code above can be translated with g++ -std=c++11 -Isingle_include doc/examples/contains_json_pointer.cpp -o contains_json_pointer See also contains(KeyT &&) const – checks the existence of a key Since version 3.7.0 Definition at line 20837 of file json.hpp.