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◆ operator[]() [5/10]
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 reference to the element at specified location idx.
- Note
- If idx is beyond the range of the array (i.e.,
idx >= size() ), then the array is silently filled up with null values to make idx a valid reference to the last stored element.
- Parameters
-
[in] | idx | index of the element to access |
- Returns
- reference to the element at index idx
- Exceptions
-
std::domain_error | if JSON is not an array or null; example: "cannot use operator[] with string" |
- Complexity\n Constant if idx is in the range of the array. Otherwise
- linear in
idx - size() .
- Example\n The example below shows how array elements can be read and
- written using
[] operator. Note the addition of null values.
11 std::cout << array[3] << '\n';
17 std::cout << array << '\n';
23 std::cout << array << '\n';
size_type size() const noexcept returns the number of elements
static basic_json array(std::initializer_list< basic_json > init=std::initializer_list< basic_json >()) explicitly create an array from an initializer list
a class to store JSON values
basic_json<> json default JSON class
Output (play with this example online):
4
[1,2,3,4,6]
[1,2,3,4,6,null,null,null,null,null,11]
The example code above can be translated with g++ -std=c++11 -Isrc doc/examples/operatorarray__size_type.cpp -o operatorarray__size_type
- Since
- version 1.0.0
Definition at line 3714 of file json.hpp.
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