std::future::get

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

 

Thread support library

Threads
thread (C++11)
this_thread namespace
get_id (C++11) yield (C++11)	sleep_for (C++11) sleep_until (C++11)
Mutual exclusion
mutex (C++11) timed_mutex (C++11)	recursive_mutex (C++11) recursive_timed_mutex (C++11)
Generic lock management
lock_guard (C++11) unique_lock (C++11) defer_lock_t try_to_lock_t adopt_lock_t (C++11) (C++11) (C++11)	lock (C++11) try_lock (C++11) defer_lock try_to_lock adopt_lock (C++11) (C++11) (C++11)
Condition variables
condition_variable (C++11)
condition_variable_any (C++11)
notify_all_at_thread_exit (C++11)
cv_status (C++11)
Futures
promise (C++11) future (C++11) shared_future (C++11) packaged_task (C++11) async (C++11)	launch (C++11) future_status (C++11) future_error (C++11) future_category (C++11) future_errc (C++11)

 

std::future

future::future

future::~future

future::operator=

future::share

Getting the result

future::get

State

future::valid

future::wait

future::wait_for

future::wait_until

 

T get();	(1)	(member only of generic future template) (since C++11)
T& get();	(2)	(member only of future<T&> template specialization) (since C++11)
void get();	(3)	(member only of future<void> template specialization) (since C++11)

The get method waits until the future has a valid result and (depending on which template is used) retrieves it. It effectively calls wait() in order to wait for the result.

The generic template and two template specializations each contain a single version of get. The three versions of get differ only in the return type.

The behavior is undefined if valid() == false before the call to this function.

valid() == false after a call to this method.

Parameters

(none)

Return value

1) The value stored in the shared state. If it satisfies the requirements of MoveAssignable, the value is moved, otherwise it is copied.

2) Reference to the value in the shared state.

3) Nothing.

Exceptions

If an exception was stored in the shared state referenced by the future (e.g. via a call to std::promise::set_exception) then that exception will be thrown.

Notes

The implementations are encouraged to detect the case when valid == false before the call and throw a future_error with an error condition of future_errc::no_state.

See also

valid	checks if the future has a shared state (public member function)