# std::experimental::observer_ptr<W>::observer_ptr

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< cpp‎ | experimental‎ | observer ptr

constexpr observer_ptr() noexcept; constexpr observer_ptr( nullptr_t ) noexcept; | (1) | (library fundamentals TS v2)
explicit observer_ptr( element_type* p ) noexcept; | (2) | (library fundamentals TS v2)
template<class W2> observer_ptr( observer_ptr<W2> other ) noexcept; | (3) | (library fundamentals TS v2)
observer_ptr( const observer_ptr& other ) = default; | (4) | (library fundamentals TS v2) (implicitly declared)
observer_ptr( observer_ptr&& other ) = default; | (5) | (library fundamentals TS v2) (implicitly declared)

1) Constructs an `observer_ptr` that has no corresponding watched object.
2) Constructs an `observer_ptr` that watches `p`.
3) Constructs an `observer_ptr` that watches `other.get()`. This constructor does not participate in overload resolution unless `W2*` is convertible to `element_type*`.
4-5) Implicitly declared copy and move constructors. Constructs an `observer_ptr` that watches `other.get()`.

### Parameters

p | - | a pointer to an object to watch
other | - | another `observer_ptr` to copy from

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