JSON for Modern C++ 3.7.3

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
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_cbor
from_cbor
from_cbor
from_msgpack
from_msgpack
from_msgpack
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
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
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
| ## ◆ items() [2/2]
iteration_proxy<iterator> nlohmann::basic_json::items | ( |  | ) |
| inlinenoexcept
  This function allows to access iterator::key() and iterator::value() during range-based for loops. In these loops, a reference to the JSON values is returned, so there is no access to the underlying iterator. For loop without `items()` function: for (auto it = j_object.begin(); it != j_object.end(); ++it) { std::cout << "key: " << it.key() << ", value:" << it.value() << '\n'; } Range-based for loop without `items()` function: for (auto it : j_object) { // "it" is of type json::reference and has no key() member std::cout << "value: " << it << '\n'; } Range-based for loop with `items()` function: for (auto& el : j_object.items()) { std::cout << "key: " << el.key() << ", value:" << el.value() << '\n'; } The `items()` function also allows to use structured bindings (C++17): for (auto& [key, val] : j_object.items()) { std::cout << "key: " << key << ", value:" << val << '\n'; } Note When iterating over an array, `key()` will return the index of the element as string (see example). For primitive types (e.g., numbers), `key()` returns an empty string. Warning Using `items()` on temporary objects is dangerous. Make sure the object's lifetime exeeds the iteration. See https://github.com/nlohmann/json/issues/2040 for more information. Returns iteration proxy object wrapping ref with an interface to use in range-based for loops Example The following code shows how the function is used. 1 #include <iostream> 2 #include <nlohmann/json.hpp> 3 4 using json = nlohmann::json; 5 6 int main() 7 { 8 // create JSON values 9 json j_object = {{"one", 1}, {"two", 2}}; 10 json j_array = {1, 2, 4, 8, 16}; 11 12 // example for an object 13 for (auto& x : j_object.items()) 14 { 15 std::cout << "key: " << x.key() << ", value: " << x.value() << '\n'; 16 } 17 18 // example for an array 19 for (auto& x : j_array.items()) 20 { 21 std::cout << "key: " << x.key() << ", value: " << x.value() << '\n'; 22 } 23 } Output (play with this example online):
      key: one, value: 1
      key: two, value: 2
      key: 0, value: 1
      key: 1, value: 2
      key: 2, value: 4
      key: 3, value: 8
      key: 4, value: 16
  The example code above can be translated with
      g++ -std=c++11 -Isingle_include doc/examples/items.cpp -o items
Exception safety Strong guarantee: if an exception is thrown, there are no changes in the JSON value. Complexity Constant. Since version 3.1.0, structured bindings support since 3.5.0. Definition at line 20651 of file json.hpp.

nlohmann::json
basic_json<> json
default JSON class
Definition: json.hpp:2774