JSON for Modern C++  3.7.3

◆ operator[]() [6/8]

const_reference nlohmann::basic_json::operator[] ( size_type  idx) const
inline

Returns a const reference to the element at specified location idx.

Parameters
[in]idxindex of the element to access
Returns
const reference to the element at index idx
Exceptions
type_error.305if the JSON value is not an array; in that case, using the [] operator with an index makes no sense.
Complexity
Constant.
Example
The example below shows how array elements can be read using the [] operator.
1 #include <iostream>
2 #include <nlohmann/json.hpp>
3 
4 using json = nlohmann::json;
5 
6 int main()
7 {
8  // create JSON array
9  json array = {"first", "2nd", "third", "fourth"};
10 
11  // output element at index 2 (third element)
12  std::cout << array.at(2) << '\n';
13 }

Output (play with this example online):
"third"
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/operatorarray__size_type_const.cpp -o operatorarray__size_type_const 
Since
version 1.0.0

Definition at line 17770 of file json.hpp.

nlohmann::basic_json::at
reference at(size_type idx)
access specified array element with bounds checking
Definition: json.hpp:17519
nlohmann::basic_json::array
static basic_json array(initializer_list_t init={})
explicitly create an array from an initializer list
Definition: json.hpp:16089
nlohmann::json
basic_json<> json
default JSON class
Definition: json.hpp:2445