C ++中模板化类型的数组

Question

我有以下内容：

QFutureWatcher<bool> *procwatcher;
procwatcher = new QFutureWatcher<bool>();
QFuture<bool> procfuture = QtConcurrent::run(this, &EraserBatch::processTile);
procwatcher->setFuture(procfuture);

  QFutureWatcher<bool> *procwatcher2;
  procwatcher2 = new QFutureWatcher<bool>();
  QFuture<bool> procfuture2 = QtConcurrent::run(this, &EraserBatch::processTile);
  procwatcher2->setFuture(procfuture2);

创建这两种类型的动态大小数组的语法是什么 - QFutureWatcher和QFuture，以便我可以说procwatcher [0]和procfuture [1]等。

谢谢！

Answer 1

只要模板完全专业化（即指定了所有模板参数），您就可以这样做：

#include <vector> // required for std::vector

std::vector<QFutureWatcher<bool>*> procWatchers;

虽然根据these documentation examples中QFutureWatcher的使用方式，您可能希望将QFutureWatcher个实例存储在std::vector中：

<击>

std::vector<QFutureWatcher<bool> > procWatchers;

这样您就不必手动new和delete QFutureWatcher个实例。

显然是QFutureWatcher inherits from QObject，uncopyable。这会阻止std::vector<QFutureWatcher<bool> >工作。

---

你有这个：

QFutureWatcher<bool> *procwatcher;
procwatcher = new QFutureWatcher<bool>();
QFuture<bool> procfuture = QtConcurrent::run(this, &EraserBatch::processTile);
procwatcher->setFuture(procfuture);

QFutureWatcher<bool> *procwatcher2;
procwatcher2 = new QFutureWatcher<bool>();
QFuture<bool> procfuture2 = QtConcurrent::run(this, &EraserBatch::processTile);
procwatcher2->setFuture(procfuture2);

您可以这样做：

// Not tested!

// Bundle QFutureWatcher and QFuture together.
template<typename T>
struct FutureStruct
{
    FutureStruct(QFutureWatcher<T>* w, const QFuture<T>& f)
        : watcher(w), future(f)
    {
        this->watcher->setFuture(this->future);
    }

    QFutureWatcher<T>* watcher; // Apparently QObjects can't be copied.
    QFuture<T> future;
};

// ...

std::vector< FutureStruct<bool> > futures;

// ...

void AddFuture()
{
    futures.push_back(FutureStruct<bool>(new QFutureWatcher<bool>(),
        QtConcurrent::run(this, &EraserBatch::processTile)));
}

// ...

futures[0].watcher; // gets you the first QFutureWatcher<bool>*
futures[0].future;  // gets you the first QFuture<bool>

futures[1].watcher; // gets you the second QFutureWatcher<bool>*
futures[1].future;  // gets you the second QFuture<bool>

// ...

当然，因为QFutureWatcher<bool>已分配new，所以在delete向量消失之前，您需要futures：

for(std::vector< FutureStruct<bool> >::iterator i = futures.begin();
    i != futures.end(); ++i)
{
    delete i->watcher;
}

Answer 2

RAII方式，如果观察者不仅由向量拥有：

typedef boost::shared_ptr<QFutureWatcher<bool> > ProcWatcherPtr;
std::vector<ProcWatcherPtr> procWatchers;

如果观察者仅由向量拥有的RAII方式：

typedef QFutureWatcher<bool> ProcWatcher
boost::ptr_vector<ProcWatcher> procWatchers;

或没有内存分配，如果它符合您的需求：

std::vector<QFutureWatcher<bool> > procWatchers;