结构
1 1..n Future<T> QFutureInterface<T> <<interface>> QFutureCallOutInterface +void postCallOutEvent(const QFutureCallOutEvent&) +void callOutInterfaceDisconnected() QFutureInterfaceBase QFutureInterfaceBasePrivate QFutureCallOutEvent
QFutureCallOutInterface ：作为QFuture处理过程中的回调
QFutureWatcher
QFutureWatcherBasePrivate是QFutureCallOutInterface的实现类
QFutureWatcher<T> QFutureWatcherBasePrivate + QList<QFutureCallOutEvent *> pendingCallOutEvents + QAtomicInt pendingResultsReady + int maximumPendingResultsReady + QAtomicInt resultAtConnected + bool finished QFutureWatcherBase -const QFutureInterfaceBase &futureInterface() -QFutureInterfaceBase &futureInterface()