Qt中parent()函数的具体使用

#pragma once

#include <QWidget>
#include "ui_QtWidgetsClass.h"

class QtWidgetsClass : public QWidget
{
	Q_OBJECT

public:
	QtWidgetsClass(QWidget *parent = nullptr);
	~QtWidgetsClass();
	void yyy();
private:
	Ui::QtWidgetsClassClass ui;
};

#include "QtWidgetsClass.h"
#include "QtWidgetsApplication1.h"
QtWidgetsClass::QtWidgetsClass(QWidget *parent)
	: QWidget(parent)
{
	ui.setupUi(this);
	connect(ui.pushButton, &QPushButton::clicked, this, &QtWidgetsClass::yyy);
}

QtWidgetsClass::~QtWidgetsClass()
{
}
void QtWidgetsClass::yyy()
{
	QtWidgetsApplication1* w = (QtWidgetsApplication1*)(this->parent());
	w->xxx();
}

#pragma once

#include <QtWidgets/QMainWindow>
#include "ui_QtWidgetsApplication1.h"

class QtWidgetsClass;
class QtWidgetsApplication1 : public QMainWindow
{
    Q_OBJECT

public:
    QtWidgetsApplication1(QWidget *parent = nullptr);
    ~QtWidgetsApplication1();
    void xxx();
private:
    Ui::QtWidgetsApplication1Class ui;
    QtWidgetsClass* c;
};

#include "QtWidgetsApplication1.h"
#include "QtWidgetsClass.h"
#include <qdebug.h>
QtWidgetsApplication1::QtWidgetsApplication1(QWidget *parent)
    : QMainWindow(parent)
{
    ui.setupUi(this);
    c = new QtWidgetsClass(this);
}

QtWidgetsApplication1::~QtWidgetsApplication1()
{
}
void QtWidgetsApplication1::xxx()
{
    qDebug() << "QtWidgetsApplication1::xxx()";
}

#include "QtWidgetsApplication1.h"
#include <QtWidgets/QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QtWidgetsApplication1 m;
    m.show();
    return a.exec();
}

QtWidgetsApplication1* w = (QtWidgetsApplication1*)(this->parent());