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◆ operator[]() [6/10]
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>
Returns a const reference to the element at specified location idx.
- Parameters
-
[in] | idx | index of the element to access |
- Returns
- const reference to the element at index idx
- Exceptions
-
std::domain_error | if JSON is not an array; example: "cannot use
operator[] with null" |
- Complexity\n Constant.
- Example\n The example below shows how array elements can be read using
- the
[] operator.
8 json array = { "first", "2nd", "third", "fourth"};
11 std::cout << array. at(2) << '\n';
static basic_json array(std::initializer_list< basic_json > init=std::initializer_list< basic_json >()) explicitly create an array from an initializer list
reference at(size_type idx) access specified array element with bounds checking
a class to store JSON values
basic_json<> json default JSON class
Output (play with this example online):
"third"
The example code above can be translated with g++ -std=c++11 -Isrc doc/examples/operatorarray__size_type_const.cpp -o operatorarray__size_type_const
- Since
- version 1.0.0
Definition at line 3760 of file json.hpp.
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