QtConcurrent给出错误

Question

根据下面的代码，我得到以下错误：

fileio.cpp:47: C3867：“FileIO：：read”：非标准语法；使用“&”创建指向成员的指针 fileio.cpp:47: error: C2780：'QFuture QtConcurrent::map(Iterator，Iterator，MapFunctor)'：期望提供3个参数-2

为什么会这样呢？

fileio.h

#ifndef FILEIO_H
#define FILEIO_H

#include <QtCore>

class FileIO : public QObject
{
    Q_OBJECT
    Q_DISABLE_COPY(FileIO)

signals:
    void finished();

public slots:
     Q_INVOKABLE void cancel();

private:
    void read(QString &fileURL);

public:
    FileIO(QObject *parent = 0);
    ~FileIO();


    Q_INVOKABLE void read_b64(const QString &fileURL);

};

#endif // FILEIO_H

fileio.cpp

#include "fileio.h"
#include <QFile>
#include <QDebug>
#include <QUrl>
#include <QThread>
#include <QtConcurrent>

FileIO::FileIO(QObject *parent)
    : QObject(parent)
{
}

FileIO::~FileIO()
{
}

void FileIO::read(QString &filePath)
{
    QByteArray finalBytes = QByteArray();

    filePath = QUrl(filePath).toLocalFile();

    QFile file(filePath);

    qDebug() << "file size: " << file.size();
    if (file.open(QIODevice::ReadOnly)) {
        finalBytes = file.readAll();
    }

    qDebug() << "byte size: " << finalBytes.length();

    //bytes.toBase64();
}


void FileIO::read_b64(const QString &filePath)
{

    QFutureWatcher<void> futureWatcher;
    QObject::connect(this, &FileIO::cancel, &futureWatcher, &QFutureWatcher<void>::cancel, Qt::UniqueConnection);
    QObject::connect(&futureWatcher, &QFutureWatcher<void>::finished, this, &FileIO::finished);


    QStringList filePaths;
    filePaths << filePath;

    QFuture<void> future = QtConcurrent::map(filePaths, this->read);

    futureWatcher.setFuture(future);
}

Answer 1

this->read无效。您希望使用std::bind将非静态成员函数与实例绑定，创建一个可调用的，然后调用QtConcurrent::map的第一次重载，使用两个参数：

QFuture<void> future =
    QtConcurrent::map(filePaths, std::bind(&FileIO::read, this));