contains() [2/2]

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 , typename std::enable_if< !std::is_same< typename std::decay< KeyT >::type, json_pointer >::value, int >::type = 0>

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

inline

check the existence of an element in a JSON object

Check whether an element exists in a JSON object with key equivalent to key. If the element is not found or the JSON value is not an object, false is returned.

Note

This method always returns false when executed on a JSON type that is not an object.

Parameters

[in]

key

key value to check its existence.

Returns

true if an element with specified key exists. If no such element with such key is found or the JSON value is not an object, false is returned.

@complexity Logarithmic in the size of the JSON object.

@liveexample{The following code shows an example for contains().,contains}

See also

see find(KeyT&&) – returns an iterator to an object element

see contains(const json_pointer&) const – checks the existence for a JSON pointer

Since

version 3.6.0

Definition at line 22307 of file json.hpp.

    {
        return is_object() && m_value.object->find(std::forward<KeyT>(key)) != m_value.object->end();
    }