json/api/basic_json_document/owns_source.md

nlohmann::basic_json_document::owns_source

bool owns_source() const noexcept;

Returns whether the document holds its own copy of the parsed text or is borrowing the caller's buffer.

Return value

#!cpp true if the document owns the text returned by source(), #!cpp false if it borrows it (or if the document is discarded).

Exception safety

No-throw guarantee: this function never throws exceptions.

Complexity

Constant.

Notes

See the ownership table on parse for which inputs are borrowed and which are owned. A borrowed document (#!cpp owns_source() == false) is only valid while the buffer it was parsed from is still alive.

Examples

??? example

```cpp
#include <iostream>
#include <string>
#include <nlohmann/json_view.hpp>

using json_document = nlohmann::json_document;

int main()
{
    std::cout << std::boolalpha;

    std::string text = R"({"a": 1})";

    // borrowed: the document only points into `text`; `text` must outlive it
    json_document borrowed = json_document::parse(text);
    std::cout << borrowed.owns_source() << '\n';

    // owned: parse_copy() always takes its own copy
    json_document copied = json_document::parse_copy(text);
    std::cout << copied.owns_source() << '\n';

    // owned: an rvalue std::string is moved in, not copied, but still owned
    json_document moved_in = json_document::parse(std::string(text));
    std::cout << moved_in.owns_source() << '\n';
}

```

Output:

```json
false
true
true

```

See also

• parse - deserialize from a compatible input
• parse_copy - deserialize a copy of a compatible input, always owned
• source - the parsed text

Version history

• Added in version 3.13.0.