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¶

true if the document owns the text returned by source(), 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 (owns_source() == false) is only valid while the buffer it was parsed from is still alive.

Examples¶

Example

#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:

false
true
true

Version history¶

Added in version 3.13.0 unreleased.