JSON for Modern C++  1.1.0
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 = int64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator>
template<typename T >
const_reference nlohmann::basic_json::operator[] ( T *  key) const
inline

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]keykey of the element to access
Returns
const reference to the element at key key
Exceptions
std::domain_errorif JSON is not an object; example: "cannot use operator[] with null"
Complexity
Logarithmic in the size of the container.
Example
The example below shows how object elements can be read using the [] operator.
1 #include <json.hpp>
2 
3 using namespace nlohmann;
4 
5 int main()
6 {
7  // create a JSON object
8  const json object =
9  {
10  {"one", 1}, {"two", 2}, {"three", 2.9}
11  };
12 
13  // output element with key "two"
14  std::cout << object["two"] << '\n';
15 }
a class to store JSON values
Definition: json.hpp:191
namespace for Niels Lohmann
Definition: json.hpp:88
Output (play with this example online):
2
The example code above can be translated with
g++ -std=c++11 -Isrc doc/examples/operatorarray__key_type_const.cpp -o operatorarray__key_type_const 
See also
at(const typename object_t::key_type&) for access by reference with range checking
value() for access by value with a default value
Since
version 1.1.0

Definition at line 3210 of file json.hpp.