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api/basic_json_document/parse_copy.md

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+# <small>nlohmann::basic_json_document::</small>parse_copy
+
+```cpp
+template<typename InputType>
+static basic_json_document parse_copy(InputType&& input,
+                                      const bool allow_exceptions = true,
+                                      const bool ignore_comments = false,
+                                      const bool ignore_trailing_commas = false);
+```
+
+Deserialize from a compatible input, always taking the document's own copy of it, regardless of the value category or
+type of `input`. Unlike [`parse()`](parse.md), the returned document never depends on `input` staying alive.
+
+## Template parameters
+
+`InputType`
+:   A compatible input; see [`parse`](parse.md#template-parameters).
+
+## Parameters
+
+`input` (in)
+:   Input to parse from.
+
+`allow_exceptions` (in)
+:   whether to throw exceptions in case of a parse error (optional, `#!cpp true` by default)
+
+`ignore_comments` (in)
+:   whether comments should be ignored and treated like whitespace (`#!cpp true`) or yield a parse error
+    (`#!cpp false`); (optional, `#!cpp false` by default)
+
+`ignore_trailing_commas` (in)
+:   whether trailing commas in arrays or objects should be ignored and treated like whitespace (`#!cpp true`) or
+    yield a parse error (`#!cpp false`); (optional, `#!cpp false` by default)
+
+## Return value
+
+The parsed document, with [`owns_source()`](owns_source.md) `#!cpp true`. If `allow_exceptions` is `#!cpp false` and
+the input is not valid JSON, the returned document is discarded; see [`is_discarded`](is_discarded.md).
+
+## Exceptions
+
+Same as [`parse`](parse.md#exceptions).
+
+## Complexity
+
+Linear in the length of the input.
+
+## Notes
+
+`parse_copy()` accepts and rejects exactly what [`parse()`](parse.md) does, and classifies numbers the same way; it
+only differs in that the input is always copied rather than sometimes borrowed. Prefer [`parse()`](parse.md) when the
+input's lifetime already covers the document's, since it avoids the copy for borrowed inputs.
+
+An integer argument that is not a `#!cpp bool` where the flags are expected, such as `#!cpp parse_copy(ptr, len)`, does not
+compile; see [`parse`](parse.md#notes).
+
+## Examples
+
+??? example
+
+    The example below returns a document from a function whose local buffer would otherwise not outlive it.
+
+    ```cpp
+    #include <iostream>
+    #include <nlohmann/json_view.hpp>
+    
+    using json_document = nlohmann::json_document;
+    
+    json_document parse_from_temporary_buffer()
+    {
+        char buffer[] = R"({"a": 1})";
+        // parse() would borrow `buffer`, which is about to go out of scope;
+        // parse_copy() takes its own copy instead, so the returned document does
+        // not depend on `buffer` afterward
+        return json_document::parse_copy(buffer);
+    }
+    
+    int main()
+    {
+        std::cout << std::boolalpha;
+    
+        json_document doc = parse_from_temporary_buffer();
+        std::cout << doc.owns_source() << '\n';
+        std::cout << doc.root().is_object() << '\n';
+    }
+    
+    ```
+
+    Output:
+
+    ```json
+    true
+    true
+    
+    ```
+
+## See also
+
+- [parse](parse.md) - deserialize from a compatible input, borrowing it where possible
+- [owns_source](owns_source.md) - return whether the document holds its own copy of the text
+
+## Version history
+
+- Added in version 3.13.0.