JSON for Modern C++ 2.0.3

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~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 = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator>
bool nlohmann::basic_json::empty | ( |  | ) | const
| inline noexcept
  Checks if a JSON value has no elements. Returns The return value depends on the different types and is defined as follows:
  Value type | return value
  --- | ---
  null | `true`
  boolean | `false`
  string | `false`
  number | `false`
  object | result of function `object_t::empty()`
  array | result of function `array_t::empty()`
  Note This function does not return whether a string stored as JSON value is empty - it returns whether the JSON container itself is empty which is false in the case of a string. Complexity Constant, as long as array_t and object_t satisfy the Container concept; that is, their `empty()` functions have constant complexity. Requirements This function helps `basic_json` satisfying the Container requirements: The complexity is constant. Has the semantics of `begin() == end()`. Example The following code uses `empty()` to check if a JSON object contains any elements. 1 #include <json.hpp> 2 3 using json = nlohmann::json; 4 5 int main() 6 { 7 // create JSON values 8 json j_null; 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 empty() 19 std::cout << std::boolalpha; 20 std::cout << j_null.empty() << '\n'; 21 std::cout << j_boolean.empty() << '\n'; 22 std::cout << j_number_integer.empty() << '\n'; 23 std::cout << j_number_float.empty() << '\n'; 24 std::cout << j_object.empty() << '\n'; 25 std::cout << j_object_empty.empty() << '\n'; 26 std::cout << j_array.empty() << '\n'; 27 std::cout << j_array_empty.empty() << '\n'; 28 std::cout << j_string.empty() << '\n'; 29 } nlohmann::json basic_json<> json default JSON class Definition: json.hpp:10512 nlohmann::basic_json::value_t::object object (unordered set of name/value pairs) nlohmann::basic_json::value_t::array array (ordered collection of values) Output (play with this example online):
      true
      false
      false
      false
      false
      true
      false
      true
      false
  The example code above can be translated with
      g++ -std=c++11 -Isrc doc/examples/empty.cpp -o empty
See also size() – returns the number of elements Since version 1.0.0 Definition at line 4622 of file json.hpp.