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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 = int64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator>
size_type nlohmann::basic_json::count | ( | typename object_t::key_type | key | ) | const
| inline
  Returns the number of elements with key key. If ObjectType is the default `std::map` type, the return value will always be `0` (key was not found) or `1` (key was found). Parameters
  [in] | key | key value of the element to count
  Returns Number of elements with key key. If the JSON value is not an object, the return value will be `0`. Complexity Logarithmic in the size of the JSON object. Example The example shows how count is used. 1 #include <json.hpp> 2 3 using namespace nlohmann; 4 5 int main() 6 { 7 // create a JSON object 8 json j_object = {{"one", 1}, {"two", 2}}; 9 10 // call find 11 auto count_two = j_object.count("two"); 12 auto count_three = j_object.count("three"); 13 14 // print values 15 std::cout << std::boolalpha; 16 std::cout << "number of elements with key \"two\": " << count_two << '\n'; 17 std::cout << "number of elements with key \"three\": " << count_three << '\n'; 18 } nlohmann::basic_json a class to store JSON values Definition: json.hpp:121 nlohmann namespace for Niels Lohmann Definition: json.hpp:56 nlohmann::basic_json::count size_type count(typename object_t::key_type key) const returns the number of occurrences of a key in a JSON object Definition: json.hpp:2763 Output:
      number of elements with key "two": 1
      number of elements with key "three": 0
  The example code above can be translated with
      g++ -std=c++11 -Isrc doc/examples/count.cpp -o count
.