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| |
| /*! |
| \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<T> 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<T> 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} |
| */ |