This constructor creates a new shared state that becomes satisfied when both rhs and rhs.get() become satisfied. If rhs is satisfied, but rhs.get() returns an invalid future then the newly created future becomes satisfied with a std::future_error exception, and the exception error code is std::future_errc::broken_promise.
Parameter
Name
Description
rhs
future< future< T > > &&
future(future< U > &&)
Creates a future from a future whose result type is convertible to this future's result type.
Parameters
Name
Description
rhs
future< U > &&
class U
typename Enable
future(std::shared_ptr< shared_state_type >)
Parameter
Name
Description
state
std::shared_ptr< shared_state_type >
Functions
get()
Waits until the shared state becomes ready, then retrieves the value stored in the shared state.
Exceptions
Type
Description
...
any exceptions stored in the shared state.
std::future_error
with std::no_state if the future does not have a shared state.
Returns
Type
Description
T
then(F &&)
Attach a continuation to the future.
Attach a callable func to be invoked when the future is ready. The return type is a future wrapping the return type of func.
Side effects: valid() == false if the operation is successful.
Parameters
Name
Description
func
F &&
a Callable to be invoked when the future is ready. The function might be called immediately, e.g., if the future is ready.
typename F
Returns
Type
Description
internal::then_helper< F, T >::future_t
future<T> where T is std::result_of_t<F, R> (basically). If T matches future<U> then it returns future<U>. The returned future will contain the result of func.
Type Aliases
shared_state_type
Alias Of: typename internal::future_base< T >::shared_state_type
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-03-05 UTC."],[[["This document outlines the features and specifications of the `future\u003cT\u003e` class, implementing the ISO/IEC TS 19571:2016 standard within the Google Cloud C++ library, spanning multiple versions, from 2.10.1 to the latest 2.37.0-rc."],["The `future\u003cT\u003e` class allows the creation of new futures from existing ones, notably including the capability to unwrap `future\u003cfuture\u003cT\u003e\u003e` and handle the potential for `std::future_error` exceptions if the inner future is invalid."],["The `get()` function is used to retrieve the value from the shared state of a `future`, with the caveat that subsequent calls to `get()` will fail as it invalidates the future upon successful retrieval, and it also highlights the potential for exceptions stored within the shared state."],["The `then(F &&)` function allows for the attachment of a continuation callable, which will be invoked when the `future` is ready, returning a new `future` that wraps the return type of the provided function."],["The `shared_state_type` is an alias of `typename internal::future_base\u003cT\u003e::shared_state_type`."]]],[]]
