Implement QPromise::timeout(msec, error)

src/qtpromise/qpromise.h

@@ -46,6 +46,9 @@ public:
     template <typename THandler>
     inline QPromise<T> tap(THandler handler) const;
 
+    template <typename E = QPromiseTimeoutException>
+    inline QPromise<T> timeout(int msec, E&& error = E()) const;
+
     inline QPromise<T> delay(int msec) const;
     inline QPromise<T> wait() const;
 

src/qtpromise/qpromise.inl

@@ -150,6 +150,26 @@ inline QPromise<T> QPromiseBase<T>::tap(THandler handler) const
     });
 }
 
+template <typename T>
+template <typename E>
+inline QPromise<T> QPromiseBase<T>::timeout(int msec, E&& error) const
+{
+    QPromise<T> p = *this;
+    return QPromise<T>([&](
+        const QPromiseResolve<T>& resolve,
+        const QPromiseReject<T>& reject) {
+
+        QTimer::singleShot(msec, [=]() {
+            // we don't need to verify the current promise state, reject()
+            // takes care of checking if the promise is already resolved,
+            // and thus will ignore this rejection.
+            reject(std::move(error));
+        });
+
+        QtPromisePrivate::PromiseFulfill<QPromise<T> >::call(p, resolve, reject);
+    });
+}
+
 template <typename T>
 inline QPromise<T> QPromiseBase<T>::delay(int msec) const
 {

src/qtpromise/qpromiseerror.h

@@ -4,6 +4,9 @@
 // QtPromise
 #include "qpromiseglobal.h"
 
+// Qt
+#include <QException>
+
 namespace QtPromise {
 
 class QPromiseError
@@ -53,6 +56,16 @@ private:
     std::exception_ptr m_exception;
 };
 
+class QPromiseTimeoutException : public QException
+{
+public:
+    void raise() const Q_DECL_OVERRIDE { throw *this; }
+    QPromiseTimeoutException* clone() const Q_DECL_OVERRIDE
+    {
+        return new QPromiseTimeoutException(*this);
+    }
+};
+
 } // namespace QtPromise
 
 #endif // QTPROMISE_QPROMISEERROR_H