QThread C++ 构造函数的初始化带 QString 参数

Question

是否可以用参数初始化一个新的QThread？我在主窗口中创建了两个线程。现在我想用 QString 初始化线程“mySave”。但这不起作用。

void MainWindow::on_startButton_clicked()
{
    thread = new QThread();
    mThread = new myThread();
    threadSave = new QThread();
    mSave = new mySave("HelloWorld");
    ....
}

我将 mSave = new mySave() 行更改为 mySave = new mySave("HelloWorld") 并将 mySave-Class 的构造函数更改为

mySave::mySave(QObject *parent, QString stringFromMainWindow)
    : QObject{parent}, m_string{stringFromMainWindow}
{
    this->stringMySave = stringFromMainWindow;
}

mySave.h

class mySave : public QObject
{
    Q_OBJECT
public:
    explicit mySave(QObject *parent = nullptr, QString stringFileName = NULL);

private:
    QFile file;
    QString m_string {};
    ....

但我变成了一个错误！

mainwindow.cpp:57:17：错误：没有匹配的构造函数来初始化“mySave” mysave.h:9:7：注意：候选构造函数（隐式复制构造函数）不可行：第一个参数没有从“const char [6]”到“const mySave”的已知转换 mysave.h:13:14：注意：候选构造函数不可行：第一个参数没有从“const char [6]”到“QObject *”的已知转换

有什么问题......？

没有 QString 参数，一切正常：

void MainWindow::on_startButton_clicked()
{
    thread = new QThread();
    mThread = new myThread();
    threadSave = new QThread();
    mSave = new mySave();

    connect(thread, SIGNAL(finished()), mThread, SLOT(deleteLater()));
    connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));

    connect(mThread, SIGNAL(emitData(const QByteArray &)), this, SLOT(setEditText(const QByteArray &)));

    mThread->moveToThread(thread);
    thread->start();

    mSave->moveToThread(threadSave);
    threadSave->start();

    QMetaObject::invokeMethod(mThread, "interfaceSerial");

    QMetaObject::invokeMethod(mSave, "startFile", Q_ARG(QString, fileName));

    qDebug() << "Main open " << QThread::currentThread();

    dataTimer.start(0); // Interval 0 means to refresh as fast as possible
}

mySave-Thread 构造函数

mySave::mySave(QObject *parent)
    : QObject{parent}
{
    qDebug() << "Thread open " << QThread::currentThread();
}

我如何在新 QThread 的构造函数中设置 QString 参数....？

谢谢&再见

Answer 1

问题解决了...你必须写

class mySave : public QObject
{
    Q_OBJECT
public:
    explicit mySave(QString stringFileName = NULL, QObject *parent = nullptr);

private:
    QFile file;

最后一个参数必须是QObject！！

Answer 2

查看您的 mySave 构造函数签名...

explicit mySave(QObject *parent = nullptr, QString stringFileName = NULL);

传递的第一个参数必须是 QObject * （或隐式可转换为 QObject * 的内容）并且传递的第二个参数必须是QString。如果您希望仅使用 QString 可以构造 mySave，那么您必须提供合适的构造函数。明显的选择是简单地反转传递参数的顺序...

explicit mySave(QString stringFileName = QString(), QObject *parent = nullptr);

话虽如此，这种性质的类最常用的构造函数调用可能是...

/* Default constructor: no text or parent. */
mySave ms1;

/* Text only. */
mySave ms2("Some text...");

/* Parent object only. */
QObject *parent = ...;
mySave ms3(parent);

/* Pass both text and parent object. */
mySave ms4("Some text...", parent);

所有这些情况都可以由以下两个构造函数提供...

mySave::mySave (const QString &stringFileName = QString(), QObject *parent = nullptr)
  : QObject(parent)
  , m_string(stringFileName)
  {
    ...
  }

mySave::mySave (QObject *parent)
  : QObject(parent)
  {
    ...
  }

或者，如果您愿意，可以将第二个设置为 委托构造函数...

mySave::mySave (QObject *parent)
  : mySave(QString(), parent)
  {}