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api/basic_json_view/basic_json_view.md

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+# <small>nlohmann::basic_json_view::</small>basic_json_view
+
+```cpp
+basic_json_view() noexcept = default;
+```
+
+Creates an invalid (discarded) view: [`type()`](type.md) is `#!cpp value_t::discarded` and
+[`is_discarded()`](is_discarded.md) is `#!cpp true`.
+
+This is the only constructor a caller can use directly. Every other view is obtained from a
+[`basic_json_document`](../basic_json_document/index.md), via [`root()`](../basic_json_document/root.md) or by
+navigating into a container with [`operator[]`](operator[].md), [`at`](at.md), [`front`](front.md), [`back`](back.md),
+[`find`](find.md), or iteration.
+
+## Exception safety
+
+No-throw guarantee: this constructor never throws exceptions.
+
+## Complexity
+
+Constant.
+
+## Notes
+
+`basic_json_view` is trivially copyable (it holds two pointers), so a default-constructed view can be used as a
+placeholder for "no value yet" and later be assigned a real view.
+
+## Examples
+
+??? example
+
+    The example below shows the default constructor and that a `basic_json_view` is a small, copyable handle.
+
+    ```cpp
+    #include <iostream>
+    #include <nlohmann/json_view.hpp>
+    
+    int main()
+    {
+        std::cout << std::boolalpha;
+    
+        // the default constructor is the only public one: it creates an invalid
+        // (discarded) view, useful as a "no value yet" placeholder
+        nlohmann::json_view v;
+        std::cout << v.is_discarded() << '\n';
+    
+        // views are trivially copyable handles (two pointers); the document owns
+        // the actual data
+        nlohmann::json_view copy = v;
+        std::cout << copy.is_discarded() << '\n';
+    }
+    
+    ```
+
+    Output:
+
+    ```json
+    true
+    true
+    
+    ```
+
+## See also
+
+- [is_discarded](is_discarded.md) - return whether the view is invalid
+- [root](../basic_json_document/root.md) - the view of a document's root value
+
+## Version history
+
+- Added in version 3.13.0.