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
| ## ◆ back() [1/2]
reference nlohmann::basic_json::back | ( |  | ) |
| inline
  Returns a reference to the last element in the container. For a JSON container `c`, the expression `c.back()` is equivalent to auto tmp = c.end(); --tmp; return *tmp; Returns In case of a structured type (array or object), a reference to the last element is returned. In case of number, string, boolean, or binary values, a reference to the value is returned. Complexity Constant. Precondition The JSON value must not be `null` (would throw `std::out_of_range`) or an empty array or object (undefined behavior, guarded by assertions). Postcondition The JSON value remains unchanged. Exceptions
  invalid_iterator.214 | when called on a `null` value. See example below.
  Example The following code shows an example for `back()`. 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_boolean = true; 10 json j_number_integer = 17; 11 json j_number_float = 23.42; 12 json j_object = {{"one", 1}, {"two", 2}}; 13 json j_object_empty(json::value_t::object); 14 json j_array = {1, 2, 4, 8, 16}; 15 json j_array_empty(json::value_t::array); 16 json j_string = "Hello, world"; 17 18 // call back() 19 std::cout << j_boolean.back() << '\n'; 20 std::cout << j_number_integer.back() << '\n'; 21 std::cout << j_number_float.back() << '\n'; 22 std::cout << j_object.back() << '\n'; 23 //std::cout << j_object_empty.back() << '\n'; // undefined behavior 24 std::cout << j_array.back() << '\n'; 25 //std::cout << j_array_empty.back() << '\n'; // undefined behavior 26 std::cout << j_string.back() << '\n'; 27 28 // back() called on a null value 29 try 30 { 31 json j_null; 32 j_null.back(); 33 } 34 catch (json::invalid_iterator& e) 35 { 36 std::cout << e.what() << '\n'; 37 } 38 } Output (play with this example online):
      true
      17
      23.42
      2
      16
      "Hello, world"
      [json.exception.invalid_iterator.214] cannot get value
  The example code above can be translated with
      g++ -std=c++11 -Isingle_include doc/examples/back.cpp -o back
See also front() – access the first element Since version 1.0.0 Definition at line 19744 of file json.hpp.

nlohmann::basic_json::invalid_iterator
detail::invalid_iterator invalid_iterator
exception indicating errors with iterators
Definition: json.hpp:16043
nlohmann::json
basic_json<> json
default JSON class
Definition: json.hpp:2774