allocator_type
array
array_t
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
basic_json
basic_json
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_pointer
const_reference
count
crbegin
crend
difference_type
dump
empty
end
end
erase
erase
erase
erase
find
find
front
front
get
get
get
get_allocator
get_ptr
get_ptr
is_array
is_boolean
is_discarded
is_null
is_number
is_number_float
is_number_integer
is_object
is_primitive
is_string
is_structured
list_init_t
max_size
number_float_t
number_integer_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[]
parse
parse
parse_event_t
parser_callback_t
pointer
push_back
push_back
push_back
rbegin
rbegin
reference
rend
rend
size
size_type
string_t
swap
swap
swap
swap
type
value_t
value_type
~basic_json

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 = int64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator>

nlohmann::basic_json::basic_json | ( | list_init_t | init,
|  | bool | type_deduction = `true`,
|  | value_t | manual_type = `value_t::array`
| ) |  |

inline

Creates a JSON value of type array or object from the passed initializer list init. In case type_deduction is `true` (default), the type of the JSON value to be created is deducted from the initializer list init according to the following rules:

1. If the list is empty, an empty JSON object value `{}` is created.
2. If the list consists of pairs whose first element is a string, a JSON object value is created where the first elements of the pairs are treated as keys and the second elements are as values.
3. In all other cases, an array is created.

The rules aim to create the best fit between a C++ initializer list and JSON values. The ratioinale is as follows:

1. The empty initializer list is written as `{}` which is exactly an empty JSON object.
2. C++ has now way of describing mapped types other than to list a list of pairs. As JSON requires that keys must be of type string, rule 2 is the weakest constraint one can pose on initializer lists to interpret them as an object.
3. In all other cases, the initializer list could not be interpreted as JSON object type, so interpreting it as JSON array type is safe.

With the rules described above, the following JSON values cannot be expressed by an initializer list:

- the empty array (`[]`): use array(list_init_t) with an empty initializer list in this case
- arrays whose elements satisfy rule 2: use array(list_init_t) with the same initializer list in this case

Note
  When used without parentheses around an empty initializer list, basic_json() is called instead of this function, yielding the JSON null value.

Parameters

  [in] | init | initializer list with JSON values
  [in] | type_deduction | internal parameter; when set to `true`, the type of the JSON value is deducted from the initializer list init; when set to `false`, the type provided via manual_type is forced. This mode is used by the functions array(list_init_t) and object(list_init_t).
  [in] | manual_type | internal parameter; when type_deduction is set to `false`, the created JSON value will use the provided type (only value_t::array and value_t::object are valid); when type_deduction is set to `true`, this parameter has no effect

Exceptions

  std::domain_error | if type_deduction is `false`, manual_type is `value_t::object`, but init contains an element which is not a pair whose first element is a string

Complexity
  Linear in the size of the initializer list init.

Example
  The example below shows how JSON values are created from initializer lists
  #include <json.hpp>
  using namespace nlohmann;
  int main()
  {
  // create JSON values
  json j_empty_init_list = json({});
  json j_object = { {"one", 1}, {"two", 2} };
  json j_array = {1, 2, 3, 4};
  json j_nested_object = { {"one", {1}}, {"two", {1, 2}} };
  json j_nested_array = { {{1}, "one"}, {{1, 2}, "two"} };
  // serialize the JSON value
  std::cout << j_empty_init_list << '\n';
  std::cout << j_object << '\n';
  std::cout << j_array << '\n';
  std::cout << j_nested_object << '\n';
  std::cout << j_nested_array << '\n';
  }
  nlohmann::json
  basic_json<> json
  default JSON class
  Definition: json.hpp:6687
  nlohmann::basic_json
  a class to store JSON values
  Definition: json.hpp:121
  nlohmann
  namespace for Niels Lohmann
  Definition: json.hpp:56
  Output (play with this example online):

      {}
      {"one":1,"two":2}
      [1,2,3,4]
      {"one":[1],"two":[1,2]}
      [[[1],"one"],[[1,2],"two"]]

  The example code above can be translated with

      g++ -std=c++11 -Isrc doc/examples/basic_json__list_init_t.cpp -o basic_json__list_init_t

See also
  basic_json array(list_init_t) - create a JSON array value from an initializer list
  basic_json object(list_init_t) - create a JSON object value from an initializer list