JSON for Modern C++ 2.1.1
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◆ operator[]() [1/10]

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>
reference nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer >::operator[] ( const json_pointer ptr)
inline

Uses a JSON pointer to retrieve a reference to the respective JSON value. No bound checking is performed. Similar to operator[](const typename object_t::key_type&), null values are created in arrays and objects if necessary.

In particular:

  • If the JSON pointer points to an object key that does not exist, it is created an filled with a null value before a reference to it is returned.
  • If the JSON pointer points to an array index that does not exist, it is created an filled with a null value before a reference to it is returned. All indices between the current maximum and the given index are also filled with null.
  • The special value - is treated as a synonym for the index past the end.
Parameters
[in]ptra JSON pointer
Returns
reference to the element pointed to by ptr
Complexity\n Constant.
Exceptions
std::out_of_rangeif the JSON pointer can not be resolved
std::domain_errorif an array index begins with '0'
std::invalid_argumentif an array index was not a number
Example\n The behavior is shown in the example. \n @includelineno operatorjson_pointer.cpp \n Output (play with this example @htmlinclude operatorjson_pointer.link):\n @verbinclude operatorjson_pointer.output \n The example code above can be translated with @verbatim g++ -std=c++11 -Isrc doc/examples/operatorjson_pointer.cpp -o operatorjson_pointer @endverbatim
Since
version 2.0.0

Definition at line 11741 of file json.hpp.