# <small>nlohmann::basic_json_document::</small>basic_json_document

```cpp
// (1)
basic_json_document() = default;

// (2)
basic_json_document(basic_json_document&& other) noexcept = default;

// (3)
basic_json_document(const basic_json_document&) = delete;
```

1. Creates an empty (discarded) document: [`root()`](root.md) returns a discarded view, and
   [`is_discarded()`](is_discarded.md) is `#!cpp true`.
2. Move constructor. Takes over `other`'s index and, if owned, its text; `other` is left as an empty document. Views
   taken from `other` before the move remain valid, because the index is heap-allocated independently of the
   `basic_json_document` object.
3. `basic_json_document` is move-only. Copying is disabled because of its cost: a copy would duplicate the whole
   index, the decoded-string buffer, and the owned text, while a move is enough in every use we know of.

## Parameters

`other` (in)
:   another document to move the index and text from

## Exception safety

No-throw guarantee: the default and move constructors never throw exceptions.

## Complexity

Constant.

## Examples

??? example

    The example below shows the default constructor and demonstrates that `basic_json_document` is move-only.

    ```cpp
    #include <iostream>
    #include <utility>
    #include <nlohmann/json_view.hpp>
    
    using json_document = nlohmann::json_document;
    
    int main()
    {
        std::cout << std::boolalpha;
    
        // the default constructor creates an empty (discarded) document
        json_document empty;
        std::cout << empty.is_discarded() << '\n';
    
        // json_document is move-only: parse() itself returns by value (moved out),
        // and a document can be moved again, e.g. into a container
        json_document doc = json_document::parse(R"({"a": 1})");
        json_document moved = std::move(doc);
        std::cout << moved.root().is_object() << '\n';
    
        // copying is disabled at compile time:
        // json_document another = moved; // does not compile
    }
    
    ```

    Output:

    ```json
    true
    true
    
    ```

## See also

- [parse](parse.md) - deserialize from a compatible input
- [is_discarded](is_discarded.md) - return whether the last parse failed

## Version history

- Added in version 3.13.0.