at() [2/6]

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>>

const_reference nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::at ( const json_pointer &  ptr ) const

inline

access specified element via JSON Pointer

Returns a const reference to the element at with specified JSON pointer ptr, with bounds checking.

Parameters

[in]

ptr

JSON pointer to the desired element

Returns

reference to the element pointed to by ptr

Exceptions

parse_error.106	if an array index in the passed JSON pointer ptr begins with '0'. See example below.
parse_error.109	if an array index in the passed JSON pointer ptr is not a number. See example below.
out_of_range.401	if an array index in the passed JSON pointer ptr is out of range. See example below.
out_of_range.402	if the array index '-' is used in the passed JSON pointer ptr. As at provides checked access (and no elements are implicitly inserted), the index '-' is always invalid. See example below.
out_of_range.403	if the JSON pointer describes a key of an object which cannot be found. See example below.
out_of_range.404	if the JSON pointer ptr can not be resolved. See example below.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

@complexity Constant.

Since

version 2.0.0

@liveexample{The behavior is shown in the example.,at_json_pointer_const}

Definition at line 26031 of file json.hpp.

    {
        return ptr.get_checked(this);
    }