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Niels Lohmann
061c30310e
- API pages for basic_json_document and basic_json_view, one per member, and for the four aliases, each with an example - features/json_view.md: the problem the view solves, ownership and lifetime, what matches basic_json::parse() and what differs, and when to choose json, ordered_json, SAX, or the view - the examples show why one would use the view, not only how: borrowed vs. owned input, reading a few fields and materializing one subtree, reusing a document across many messages - registered in the mkdocs navigation, llms.txt, the docset, the exceptions page (out_of_range.416), architecture.md, the integration page, and the README; the yyjson credit is added to the README and license.md Signed-off-by: Niels Lohmann <mail@nlohmann.me>
34 lines
1.1 KiB
C++
34 lines
1.1 KiB
C++
#include <iostream>
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#include <string>
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#include <utility>
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#include <nlohmann/json_view.hpp>
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using json_document = nlohmann::json_document;
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int main()
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{
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std::cout << std::boolalpha;
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// BORROWED: doc only points into `text`; `text` must outlive `doc`
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std::string text = R"({"a": 1})";
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json_document doc = json_document::parse(text);
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std::cout << doc.owns_source() << '\n'; // false
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// a view is valid as long as the document is alive, has not been
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// re-parsed (read()) or shrunk (shrink_to_fit()), and -- if borrowed --
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// the source text is alive
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nlohmann::json_view v = doc.root();
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std::cout << v.is_object() << '\n';
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// re-parsing the SAME document invalidates views taken before the call;
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// `v` above must not be used after this line
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doc.read(R"([1, 2, 3])");
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v = doc.root(); // take a fresh view instead
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std::cout << v.is_array() << '\n';
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// moving the document does not invalidate views: the node index is
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// heap-allocated and does not move with the document object
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json_document moved = std::move(doc);
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std::cout << v.is_array() << '\n';
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}
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