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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
//! [0]
extern void aFunction();
QFuture<void> future = QtConcurrent::run(aFunction);
//! [0]
//! [explicit-pool-0]
extern void aFunction();
QThreadPool pool;
QFuture<void> future = QtConcurrent::run(&pool, aFunction);
//! [explicit-pool-0]
//! [1]
extern void aFunctionWithArguments(int arg1, double arg2, const QString &string);
int integer = ...;
double floatingPoint = ...;
QString string = ...;
QFuture<void> future = QtConcurrent::run(aFunctionWithArguments, integer, floatingPoint, string);
//! [1]
//! [2]
extern QString functionReturningAString();
QFuture<QString> future = QtConcurrent::run(functionReturningAString);
...
QString result = future.result();
//! [2]
//! [3]
extern QString someFunction(const QByteArray &input);
QByteArray bytearray = ...;
QFuture<QString> future = QtConcurrent::run(someFunction, bytearray);
...
QString result = future.result();
//! [3]
//! [4]
// call 'QList<QByteArray> QByteArray::split(char sep) const' in a separate thread
QByteArray bytearray = "hello world";
QFuture<QList<QByteArray> > future = QtConcurrent::run(&QByteArray::split, bytearray, ' ');
...
QList<QByteArray> result = future.result();
//! [4]
//! [5]
// call 'void QImage::invertPixels(InvertMode mode)' in a separate thread
QImage image = ...;
QFuture<void> future = QtConcurrent::run(&QImage::invertPixels, &image, QImage::InvertRgba);
...
future.waitForFinished();
// At this point, the pixels in 'image' have been inverted
//! [5]
//! [6]
QFuture<void> future = QtConcurrent::run([=]() {
// Code in this block will run in another thread
});
...
//! [6]
//! [7]
static void addOne(int &n) { ++n; }
...
int n = 42;
QtConcurrent::run(&addOne, std::ref(n)).waitForFinished(); // n == 43
//! [7]
//! [8]
struct TestClass
{
void operator()(int s1) { s = s1; }
int s = 42;
};
...
TestClass o;
// Modify original object
QtConcurrent::run(std::ref(o), 15).waitForFinished(); // o.s == 15
// Modify a copy of the original object
QtConcurrent::run(o, 42).waitForFinished(); // o.s == 15
// Use a temporary object
QtConcurrent::run(TestClass(), 42).waitForFinished();
// Ill-formed
QtConcurrent::run(&o, 42).waitForFinished(); // compilation error
//! [8]
//! [9]
extern void aFunction(QPromise<void> &promise);
QFuture<void> future = QtConcurrent::run(aFunction);
//! [9]
//! [10]
extern void aFunction(QPromise<void> &promise, int arg1, const QString &arg2);
int integer = ...;
QString string = ...;
QFuture<void> future = QtConcurrent::run(aFunction, integer, string);
//! [10]
//! [11]
void helloWorldFunction(QPromise<QString> &promise)
{
promise.addResult("Hello");
promise.addResult("world");
}
QFuture<QString> future = QtConcurrent::run(helloWorldFunction);
...
QList<QString> results = future.results();
//! [11]
//! [12]
void aFunction(QPromise<int> &promise)
{
for (int i = 0; i < 100; ++i) {
promise.suspendIfRequested();
if (promise.isCanceled())
return;
// computes the next result, may be time consuming like 1 second
const int res = ... ;
promise.addResult(res);
}
}
QFuture<int> future = QtConcurrent::run(aFunction);
... // user pressed a pause button after 10 seconds
future.suspend();
... // user pressed a resume button after 10 seconds
future.resume();
... // user pressed a cancel button after 10 seconds
future.cancel();
//! [12]
//! [13]
void aFunction(QPromise<int> &promise)
{
promise.setProgressRange(0, 100);
int result = 0;
for (int i = 0; i < 100; ++i) {
// computes some part of the task
const int part = ... ;
result += part;
promise.setProgressValue(i);
}
promise.addResult(result);
}
QFutureWatcher<int> watcher;
QObject::connect(&watcher, &QFutureWatcher::progressValueChanged, [](int progress){
... ; // update GUI with a progress
qDebug() << "current progress:" << progress;
});
watcher.setFuture(QtConcurrent::run(aFunction));
//! [13]
//! [14]
struct Functor {
void operator()(QPromise<int> &) { }
void operator()(QPromise<double> &) { }
};
Functor f;
run<double>(f); // this will select the 2nd overload
// run(f); // error, both candidate overloads potentially match
//! [14]
//! [15]
void foo(int arg);
void foo(int arg1, int arg2);
...
QFuture<void> future = QtConcurrent::run(foo, 42);
//! [15]
//! [16]
QFuture<void> future = QtConcurrent::run([] { foo(42); });
//! [16]
//! [17]
QFuture<void> future = QtConcurrent::run(static_cast<void(*)(int)>(foo), 42);
//! [17]
//! [18]
QFuture<void> future = QtConcurrent::run(qOverload<int>(foo), 42);
//! [18]