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Please review the following ** information to ensure the GNU General Public License requirements will ** be met: https://www.gnu.org/licenses/gpl-2.0.html and ** https://www.gnu.org/licenses/gpl-3.0.html. ** ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \page qtconcurrentrun.html \title Concurrent Run \ingroup thread The QtConcurrent::run() function runs a function in a separate thread. The return value of the function is made available through the QFuture API. This function is a part of the \l {Qt Concurrent} framework. \section1 Running a Function in a Separate Thread To run a function in another thread, use QtConcurrent::run(): \snippet code/src_concurrent_qtconcurrentrun.cpp 0 This will run \e aFunction in a separate thread obtained from the default QThreadPool. You can use the QFuture and QFutureWatcher classes to monitor the status of the function. To use a dedicated thread pool, you can pass the QThreadPool as the first argument: \snippet code/src_concurrent_qtconcurrentrun.cpp explicit-pool-0 \section1 Passing Arguments to the Function Passing arguments to the function is done by adding them to the QtConcurrent::run() call immediately after the function name. For example: \snippet code/src_concurrent_qtconcurrentrun.cpp 1 A copy of each argument is made at the point where QtConcurrent::run() is called, and these values are passed to the thread when it begins executing the function. Changes made to the arguments after calling QtConcurrent::run() are \e not visible to the thread. \section1 Returning Values from the Function Any return value from the function is available via QFuture: \snippet code/src_concurrent_qtconcurrentrun.cpp 2 As documented above, passing arguments is done like this: \snippet code/src_concurrent_qtconcurrentrun.cpp 3 Note that the QFuture::result() function blocks and waits for the result to become available. Use QFutureWatcher to get notification when the function has finished execution and the result is available. \section1 Additional API Features \section2 Using Member Functions QtConcurrent::run() also accepts pointers to member functions. The first argument must be either a const reference or a pointer to an instance of the class. Passing by const reference is useful when calling const member functions; passing by pointer is useful for calling non-const member functions that modify the instance. For example, calling QByteArray::split() (a const member function) in a separate thread is done like this: \snippet code/src_concurrent_qtconcurrentrun.cpp 4 Calling a non-const member function is done like this: \snippet code/src_concurrent_qtconcurrentrun.cpp 5 \section2 Using Lambda Functions Calling a lambda function is done like this: \snippet code/src_concurrent_qtconcurrentrun.cpp 6 */ /*! \typedef Function \internal This typedef is a dummy required to make the \c Function type name known so that clang doesn't reject functions that use it. */ /*! \fn QFuture QtConcurrent::run(Function function, ...); Equivalent to \code QtConcurrent::run(QThreadPool::globalInstance(), function, ...); \endcode Runs \a function in a separate thread. The thread is taken from the global QThreadPool. Note that \a function may not run immediately; \a function will only be run once a thread becomes available. T is the same type as the return value of \a function. Non-void return values can be accessed via the QFuture::result() function. \note The QFuture returned can only be used to query for the running/finished status and the return value of the function. In particular, canceling or pausing can be issued only if the computations behind the future has not been started. \sa {Concurrent Run} */ /*! \since 5.4 \fn QFuture QtConcurrent::run(QThreadPool *pool, Function function, ...); Runs \a function in a separate thread. The thread is taken from the QThreadPool \a pool. Note that \a function may not run immediately; \a function will only be run once a thread becomes available. T is the same type as the return value of \a function. Non-void return values can be accessed via the QFuture::result() function. \note The QFuture returned can only be used to query for the running/finished status and the return value of the function. In particular, canceling or pausing can be issued only if the computations behind the future has not been started. \sa {Concurrent Run} */