operator[]() [8/8]

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 T >

const_reference nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::operator[] ( T *  key ) const

inline

read-only access specified object element

Returns a const reference to the element at with specified key key. No bounds checking is performed.

Warning

If the element with key key does not exist, the behavior is undefined.

Parameters

[in]

key

key of the element to access

Returns

const reference to the element at key key

Precondition

The element with key key must exist. This precondition is enforced with an assertion.

Exceptions

type_error.305

if the JSON value is not an object; in that case, using the [] operator with a key makes no sense.

@complexity Logarithmic in the size of the container.

@liveexample{The example below shows how object elements can be read using the [] operator.,operatorarray__key_type_const}

See also

see at(const typename object_t::key_type&) for access by reference with range checking

see value() for access by value with a default value

Since

version 1.1.0

Definition at line 21616 of file json.hpp.

    {
        // at only works for objects
        if (JSON_HEDLEY_LIKELY(is_object()))
        {
            JSON_ASSERT(m_value.object->find(key) != m_value.object->end());
            return m_value.object->find(key)->second;
        }
 
        JSON_THROW(type_error::create(305, "cannot use operator[] with a string argument with " + std::string(type_name()), *this));
    }