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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>
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
- Constant if idx is in the range of the array. Otherwise linear in
idx - size() .
- Example
- The example below shows how array elements can be read and written using
[] operator. Note the addition of null values. 8 json array = {1, 2, 3, 4, 5}; 11 std::cout << array[3] << '\n'; 14 array[array.size() - 1] = 6; 17 std::cout << array << '\n'; 23 std::cout << array << '\n'; 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 withg++ -std=c++11 -Isrc doc/examples/operatorarray__size_type.cpp -o operatorarray__size_type
- Since
- version 1.0.0
Definition at line 3226 of file json.hpp.
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