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, class BinaryType = std::vector<std::uint8_t>>

template<typename KeyT >

size_type nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::count ( KeyT &&  key ) const

inline

returns the number of occurrences of a key in a JSON object

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]

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.

@liveexample{The example shows how count() is used.,count}

Since

version 1.0.0

Definition at line 22274 of file json.hpp.

    {
        // return 0 for all nonobject types
        return is_object() ? m_value.object->count(std::forward<KeyT>(key)) : 0;
    }