deploy: 4155e2938f

examples/json_view_ownership.cpp

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+#include <iostream>
+#include <string>
+#include <utility>
+#include <nlohmann/json_view.hpp>
+
+using json_document = nlohmann::json_document;
+
+int main()
+{
+    std::cout << std::boolalpha;
+
+    // BORROWED: doc only points into `text`; `text` must outlive `doc`
+    std::string text = R"({"a": 1})";
+    json_document doc = json_document::parse(text);
+    std::cout << doc.owns_source() << '\n'; // false
+
+    // a view is valid as long as the document is alive, has not been
+    // re-parsed (read()) or shrunk (shrink_to_fit()), and -- if borrowed --
+    // the source text is alive
+    nlohmann::json_view v = doc.root();
+    std::cout << v.is_object() << '\n';
+
+    // re-parsing the SAME document invalidates views taken before the call;
+    // `v` above must not be used after this line
+    doc.read(R"([1, 2, 3])");
+    v = doc.root(); // take a fresh view instead
+    std::cout << v.is_array() << '\n';
+
+    // moving the document does not invalidate views: the node index is
+    // heap-allocated and does not move with the document object
+    json_document moved = std::move(doc);
+    std::cout << v.is_array() << '\n';
+}