QtFuture 名称空间

包含的杂项标识符可用于 QFuture 类。更多...

头：	#include < QFuture >
CMake:	find_package(Qt6 REQUIRED COMPONENTS Core) target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake:	QT += core

类

struct

WhenAnyResult

类型

enum class

Launch { Sync, Async, Inherit }

函数

QFuture<ArgsType<Signal>>	connect (Sender * sender , Signal signal )
QFuture<T>	makeExceptionalFuture (const QException & exception )
QFuture<T>	makeExceptionalFuture (std::exception_ptr exception )
QFuture<std::decay_t<T>>	makeReadyFuture (T && value )
QFuture<void>	makeReadyFuture ()
QFuture<T>	makeReadyFuture (const QList<T> & values )
QFuture<OutputSequence>	whenAll (InputIt first , InputIt last )
QFuture<OutputSequence>	whenAll (Futures &&... futures )
QFuture<QtFuture::WhenAnyResult<T>>	whenAny (InputIt first , InputIt last )
QFuture<std::variant<std::decay_t<Futures>...>>	whenAny (Futures &&... futures )

详细描述

类

class WhenAnyResult

QtFuture::WhenAnyResult is used to represent the result of QtFuture::whenAny (). 更多...

类型文档编制

`[since 6.0]` enum class QtFuture:: Launch

Represents execution policies for running a QFuture continuation.

常量	值	描述
`QtFuture::Launch::Sync`	`0`	The continuation will be launched in the same thread that fulfills the promise associated with the future to which the continuation was attached, or if it has already finished, the continuation will be invoked immediately, in the thread that executes `then()` .
`QtFuture::Launch::Async`	`1`	The continuation will be launched in a separate thread taken from the global QThreadPool .
`QtFuture::Launch::Inherit`	`2`	The continuation will inherit the launch policy or thread pool of the future to which it is attached.

Sync is used as a default launch policy.

该枚举在 Qt 6.0 引入 (或被修改)。

另请参阅 QFuture::then () 和 QThreadPool::globalInstance ().

函数文档编制

template <typename Sender, typename Signal, typename> QFuture < ArgsType < 信号 >> QtFuture:: connect ( Sender * sender , 信号 signal )

创建并返回 QFuture which will become available when the sender 发射 signal 。若 signal takes no arguments, a QFuture <void> is returned. If the signal takes a single argument, the resulted QFuture will be filled with the signal's argument value. If the signal takes multiple arguments, the resulted QFuture is filled with std::tuple storing the values of signal's arguments. If the sender is destroyed before the signal is emitted, the resulted QFuture will be canceled.

For example, let's say we have the following object:

class Object : public QObject
{
    Q_OBJECT
    ...
signals:
    void noArgSignal();
    void singleArgSignal(int value);
    void multipleArgs(int value1, double value2, const QString &value3);
};

We can connect its signals to QFuture objects in the following way:

Object object;
QFuture<void> voidFuture = QtFuture::connect(&object, &Object::noArgSignal);
QFuture<int> intFuture = QtFuture::connect(&object, &Object::singleArgSignal);
using Args = std::tuple<int, double, QString>;
QFuture<Args> tupleFuture = QtFuture::connect(&object, &Object::multipleArgs)

We can also chain continuations to be run when a signal is emitted:

QtFuture::connect(&object, &Object::singleArgSignal).then([](int value) {
    // do something with the value
});

You can also start the continuation in a new thread or a custom thread pool using QtFuture::Launch policies. For example:

QtFuture::connect(&object, &Object::singleArgSignal).then(QtFuture::Launch::Async, [](int value) {
    // this will run in a new thread
});

Throwing an exception from a slot invoked by Qt's signal-slot connection is considered to be an undefined behavior, if it is not handled within the slot. But with QFuture::connect(), you can throw and handle exceptions from the continuations:

QtFuture::connect(&object, &Object::singleArgSignal).then([](int value) {
    ...
    throw std::exception();
    ...
}).onFailed([](const std::exception &e) {
    // handle the exception
}).onFailed([] {
    // handle other exceptions
});

注意： The connected future will be fulfilled only once, when the signal is emitted for the first time.

另请参阅 QFuture and QFuture::then ().

`[since 6.1]` template <typename T> QFuture < T > QtFuture:: makeExceptionalFuture (const QException & exception )

创建并返回 QFuture which already has an exception exception .

QException e;
auto f = QtFuture::makeExceptionalFuture<int>(e);
...
try {
    f.result(); // throws QException
} catch (QException &) {
    // handle exception here
}

该函数在 Qt 6.1 引入。

另请参阅 QFuture , QException ，和 QtFuture::makeReadyFuture ().

`[since 6.1]` template <typename T> QFuture < T > QtFuture:: makeExceptionalFuture ( std::exception_ptr exception )

这是重载函数。

创建并返回 QFuture which already has an exception exception .

struct TestException
{
};
...
auto exception = std::make_exception_ptr(TestException());
auto f = QtFuture::makeExceptionalFuture<int>(exception);
...
try {
    f.result(); // throws TestException
} catch (TestException &) {
    // handle exception here
}

该函数在 Qt 6.1 引入。

另请参阅 QFuture , QException ，和 QtFuture::makeReadyFuture ().

`[since 6.1]` template <typename T, typename> QFuture < std::decay_t < T >> QtFuture:: makeReadyFuture ( T && value )

这是重载函数。

创建并返回 QFuture which already has a result value . The returned QFuture has a type of std::decay_t<T>, where T is not void.

auto f = QtFuture::makeReadyFuture(std::make_unique<int>(42));
...
const int result = *f.takeResult(); // result == 42

该函数在 Qt 6.1 引入。

另请参阅 QFuture and QtFuture::makeExceptionalFuture ().

`[since 6.1]` QFuture < void > QtFuture:: makeReadyFuture ()

这是重载函数。

Creates and returns a void QFuture . Such QFuture can't store any result. One can use it to query the state of the computation. The returned QFuture will always be in the finished state.

auto f = QtFuture::makeReadyFuture();
...
const bool started = f.isStarted(); // started == true
const bool running = f.isRunning(); // running == false
const bool finished = f.isFinished(); // finished == true

该函数在 Qt 6.1 引入。

另请参阅 QFuture , QFuture::isStarted (), QFuture::isRunning (), QFuture::isFinished ()，和 QtFuture::makeExceptionalFuture ().

`[since 6.1]` template <typename T> QFuture < T > QtFuture:: makeReadyFuture (const QList < T > & values )

这是重载函数。

创建并返回 QFuture which already has multiple results set from values .

const QList<int> values { 1, 2, 3 };
auto f = QtFuture::makeReadyFuture(values);
...
const int count = f.resultCount(); // count == 3
const auto results = f.results(); // results == { 1, 2, 3 }

该函数在 Qt 6.1 引入。

另请参阅 QFuture and QtFuture::makeExceptionalFuture ().

`[since 6.3]` template <typename OutputSequence, typename InputIt> QFuture < OutputSequence > QtFuture:: whenAll ( InputIt first , InputIt last )

返回新的 QFuture that succeeds when all futures from first to last complete. first and last are iterators to a sequence of futures packaging type T . OutputSequence is a sequence containing all completed futures from first to last , appearing in the same order as in the input. If the type of OutputSequence is not specified, the resulting futures will be returned in a QList of QFuture<T> 。例如：

QList<QFuture<int>> inputFutures {...};
// whenAll has type QFuture<QList<QFuture<int>>>
auto whenAll = QtFuture::whenAll(inputFutures.begin(), inputFutures.end());
// whenAllVector has type QFuture<std::vector<QFuture<int>>>
auto whenAllVector =
        QtFuture::whenAll<std::vector<QFuture<int>>>(inputFutures.begin(), inputFutures.end());

注意： The output sequence must support random access and the resize() 操作。

若 first 等于 last , this function returns a ready QFuture that contains an empty OutputSequence .

The returned future always completes successfully after all the specified futures complete. It doesn't matter if any of these futures completes with error or is canceled. You can use .then() to process the completed futures after the future returned by whenAll() succeeds:

QList<QFuture<int>> inputFutures {...};
QtFuture::whenAll(inputFutures.begin(), inputFutures.end())
        .then([](const QList<QFuture<int>> &results) {
            for (auto future : results) {
                if (future.isCanceled())
                    // handle the cancellation (possibly due to an exception)
                else
                    // do something with the result
            }
        });

注意： If the input futures complete on different threads, the future returned by this method will complete in the thread that the last future completes in. Therefore, the continuations attached to the future returned by whenAll() cannot always make assumptions about which thread they will be run on. Use the overload of .then() that takes a context object if you want to control which thread the continuations are invoked on.

该函数在 Qt 6.3 引入。

`[since 6.3]` template <typename OutputSequence, typename Futures> QFuture < OutputSequence > QtFuture:: whenAll ( Futures &&... futures )

返回新的 QFuture that succeeds when all futures packaging arbitrary types complete. OutputSequence is a sequence of completed futures. The type of its entries is std::variant<Futures...> . For each QFuture<T> passed to whenAll() , the entry at the corresponding position in OutputSequence will be a std::variant holding that QFuture<T> , in its completed state. If the type of OutputSequence is not specified, the resulting futures will be returned in a QList of std::variant<Futures...> 。例如：

QFuture<int> intFuture = ...;
QFuture<QString> stringFuture = ...;
QFuture<void> voidFuture = ...;
using FuturesVariant = std::variant<QFuture<int>, QFuture<QString>, QFuture<void>>;
// whenAll has type QFuture<QList<FuturesVariant>>
auto whenAll = QtFuture::whenAll(intFuture, stringFuture, voidFuture);
// whenAllVector has type QFuture<std::vector<FuturesVariant>>
auto whenAllVector =
        QtFuture::whenAll<std::vector<FuturesVariant>>(intFuture, stringFuture, voidFuture);

注意： The output sequence should support random access and the resize() 操作。

QFuture<int> intFuture = ...;
QFuture<QString> stringFuture = ...;
QFuture<void> voidFuture = ...;
using FuturesVariant = std::variant<QFuture<int>, QFuture<QString>, QFuture<void>>;
QtFuture::whenAll(intFuture, stringFuture, voidFuture)
        .then([](const QList<FuturesVariant> &results) {
            ...
            for (auto result : results)
            {
                // assuming handleResult() is overloaded based on the QFuture type
                std::visit([](auto &&future) { handleResult(future); }, result);
            }
            ...
        });

该函数在 Qt 6.3 引入。

`[since 6.3]` template <typename T, typename InputIt> QFuture < QtFuture::WhenAnyResult < T >> QtFuture:: whenAny ( InputIt first , InputIt last )

返回新的 QFuture that succeeds when any of the futures from first to last completes. first and last are iterators to a sequence of futures packaging type T . The returned future packages a value of type QtFuture::WhenAnyResult<T> which in turn packages the index of the first completed QFuture 和 QFuture itself. If first 等于 last , this function returns a ready QFuture that has -1 为 index field in the QtFuture::WhenAnyResult struct and a default-constructed QFuture<T> 为 future field. Note that a default-constructed QFuture is a completed future in a cancelled state.

The returned future always completes successfully after the first future from the specified futures completes. It doesn't matter if the first future completes with error or is canceled. You can use .then() to process the result after the future returned by whenAny() succeeds:

QList<QFuture<int>> inputFutures = ...;
QtFuture::whenAny(inputFutures.begin(), inputFutures.end())
        .then([](const QtFuture::WhenAnyResult<int> &result) {
            qsizetype index = result.index;
            QFuture<int> future = result.future;
            // ...
        });

注意： If the input futures complete on different threads, the future returned by this method will complete in the thread that the first future completes in. Therefore, the continuations attached to the future returned by whenAny() cannot always make assumptions about which thread they will be run on. Use the overload of .then() that takes a context object if you want to control which thread the continuations are invoked on.

该函数在 Qt 6.3 引入。

另请参阅 QtFuture::WhenAnyResult .

`[since 6.3]` template <typename Futures> QFuture < std::variant < std::decay_t < Futures >...>> QtFuture:: whenAny ( Futures &&... futures )

返回新的 QFuture that succeeds when any of the futures completes. futures can package arbitrary types. The returned future packages the value of type std::variant<Futures...> which in turn packages the first completed QFuture from futures 。可以使用 std::variant::index() to find out the index of the future in the sequence of futures that finished first.

QFuture<int> intFuture = ...;
QFuture<QString> stringFuture = ...;
QFuture<void> voidFuture = ...;
using FuturesVariant = std::variant<QFuture<int>, QFuture<QString>, QFuture<void>>;
QtFuture::whenAny(intFuture, stringFuture, voidFuture).then([](const FuturesVariant &result) {
    ...
    // assuming handleResult() is overloaded based on the QFuture type
    std::visit([](auto &&future) { handleResult(future); }, result);
    ...
});

该函数在 Qt 6.3 引入。

QtFuture 名称空间

类

类型

函数

详细描述

类

class WhenAnyResult

类型文档编制

[since 6.0] enum class QtFuture:: Launch

函数文档编制

template <typename Sender, typename Signal, typename> QFuture < ArgsType < 信号 >> QtFuture:: connect ( Sender * sender , 信号 signal )

[since 6.1] template <typename T> QFuture < T > QtFuture:: makeExceptionalFuture (const QException & exception )

[since 6.1] template <typename T> QFuture < T > QtFuture:: makeExceptionalFuture ( std::exception_ptr exception )

[since 6.1] template <typename T, typename> QFuture < std::decay_t < T >> QtFuture:: makeReadyFuture ( T && value )

[since 6.1] QFuture < void > QtFuture:: makeReadyFuture ()

[since 6.1] template <typename T> QFuture < T > QtFuture:: makeReadyFuture (const QList < T > & values )

[since 6.3] template <typename OutputSequence, typename InputIt> QFuture < OutputSequence > QtFuture:: whenAll ( InputIt first , InputIt last )

[since 6.3] template <typename OutputSequence, typename Futures> QFuture < OutputSequence > QtFuture:: whenAll ( Futures &&... futures )

[since 6.3] template <typename T, typename InputIt> QFuture < QtFuture::WhenAnyResult < T >> QtFuture:: whenAny ( InputIt first , InputIt last )

[since 6.3] template <typename Futures> QFuture < std::variant < std::decay_t < Futures >...>> QtFuture:: whenAny ( Futures &&... futures )

内容

`[since 6.0]` enum class QtFuture:: Launch

`[since 6.1]` template <typename T> QFuture < T > QtFuture:: makeExceptionalFuture (const QException & exception )

`[since 6.1]` template <typename T> QFuture < T > QtFuture:: makeExceptionalFuture ( std::exception_ptr exception )

`[since 6.1]` template <typename T, typename> QFuture < std::decay_t < T >> QtFuture:: makeReadyFuture ( T && value )

`[since 6.1]` QFuture < void > QtFuture:: makeReadyFuture ()

`[since 6.1]` template <typename T> QFuture < T > QtFuture:: makeReadyFuture (const QList < T > & values )

`[since 6.3]` template <typename OutputSequence, typename InputIt> QFuture < OutputSequence > QtFuture:: whenAll ( InputIt first , InputIt last )

`[since 6.3]` template <typename OutputSequence, typename Futures> QFuture < OutputSequence > QtFuture:: whenAll ( Futures &&... futures )

`[since 6.3]` template <typename T, typename InputIt> QFuture < QtFuture::WhenAnyResult < T >> QtFuture:: whenAny ( InputIt first , InputIt last )

`[since 6.3]` template <typename Futures> QFuture < std::variant < std::decay_t < Futures >...>> QtFuture:: whenAny ( Futures &&... futures )