mirror of
https://github.com/nlohmann/json.git
synced 2026-09-16 13:17:59 +00:00
74 lines
2.1 KiB
Markdown
74 lines
2.1 KiB
Markdown
# <small>nlohmann::basic_json::</small>array_t
|
|
|
|
```cpp
|
|
using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
|
|
```
|
|
|
|
The type used to store JSON arrays.
|
|
|
|
[RFC 8259](https://tools.ietf.org/html/rfc8259) describes JSON arrays as follows:
|
|
> An array is an ordered sequence of zero or more values.
|
|
|
|
To store objects in C++, a type is defined by the template parameters explained below.
|
|
|
|
## Template parameters
|
|
|
|
`ArrayType`
|
|
: container type to store arrays. It must be a vector-like container: the library uses `operator[]`, `at()`, and
|
|
`resize()`, and requires random-access iterators. `#!cpp std::vector` and `#!cpp std::deque` qualify;
|
|
`#!cpp std::list` does not. See
|
|
[Template Parameter Requirements](../../features/types/template_parameters.md#arraytype) for the full list of
|
|
requirements.
|
|
|
|
`AllocatorType`
|
|
: the allocator to use for objects (e.g., `std::allocator`)
|
|
|
|
## Notes
|
|
|
|
#### Default type
|
|
|
|
With the default values for `ArrayType` (`std::vector`) and `AllocatorType` (`std::allocator`), the default value for
|
|
`array_t` is:
|
|
|
|
```cpp
|
|
std::vector<
|
|
basic_json, // value_type
|
|
std::allocator<basic_json> // allocator_type
|
|
>
|
|
```
|
|
|
|
#### Limits
|
|
|
|
[RFC 8259](https://tools.ietf.org/html/rfc8259) specifies:
|
|
> An implementation may set limits on the maximum depth of nesting.
|
|
|
|
In this class, the array's limit of nesting is not explicitly constrained. However, a maximum depth of nesting may be
|
|
introduced by the compiler or runtime environment. A theoretical limit can be queried by calling the
|
|
[`max_size`](max_size.md) function of a JSON array.
|
|
|
|
#### Storage
|
|
|
|
Arrays are stored as pointers in a `basic_json` type. That is, for any access to array values, a pointer of type
|
|
`#!cpp array_t*` must be dereferenced.
|
|
|
|
## Examples
|
|
|
|
??? example
|
|
|
|
The following code shows that `array_t` is by default, a typedef to `#!cpp std::vector<nlohmann::json>`.
|
|
|
|
```cpp
|
|
--8<-- "examples/array_t.cpp"
|
|
```
|
|
|
|
Output:
|
|
|
|
```json
|
|
--8<-- "examples/array_t.output"
|
|
```
|
|
|
|
## Version history
|
|
|
|
- Added in version 1.0.0.
|
|
- Made `capacity()` optional, so that array types such as `#!cpp std::deque` can be used, in version 3.13.0.
|