< cpp‎ | thread‎ | future

bool valid() const;
(since C++11)

Checks if the future refers to a shared state.

This is the case only for futures that were not default-constructed or moved from (i.e. returned by std::promise::get_future(), std::packaged_task::get_future() or std::async()) until the first time get() or share() is called.

The behavior is undefined if any member function other than the destructor, the move-assignment operator, or valid is called on a future that does not refer to shared state (although implementations are encouraged to throw std::future_error indicating no_state in this case). It is valid to move from a future object for which valid() is false



Return value

true if *this refers to a shared state, otherwise false.


noexcept specification:  


See also

waits for the result to become available
(public member function)