JSON for Modern C++  3.5.0

◆ count()

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, template< typename T, typename SFINAE=void > class JSONSerializer = adl_serializer>
template<typename KeyT >
size_type nlohmann::basic_json::count ( KeyT &&  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).

Note
This method always returns 0 when executed on a JSON type that is not an object.
Parameters
[in]keykey 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. ^^ count.cpp
Output (play with this example online):^^
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 -Isingle_include doc/examples/count.cpp -o count 
Since
version 1.0.0

Definition at line 16346 of file json.hpp.