Q_OBJECT与否Q_OBJECT [英] Q_OBJECT or not Q_OBJECT

问题描述

我在main.cpp中编写了一个带有自己的类的小程序.这里的代码:

I wrote a little program with a my own class within the main.cpp. Here the code:

#include <QApplication>
#include <QPushButton>
#include <QLabel>

class MyWidget : public QWidget {
    //Q_OBJECT
public:
    MyWidget(QWidget* parent = 0);
    QLabel* label;
    QString string;

signals:
public slots:
    void setTextLabel();

};

void MyWidget::setTextLabel() {
    label->setText("Test");
}


MyWidget::MyWidget(QWidget* parent) 
     : QWidget(parent) {

}

int main(int argc, char** argv) {
    QApplication app(argc, argv);

    MyWidget widget;
    widget.show();

    return app.exec();
}

似乎可以工作，但不能完全"使用.我的广告位无效.我想我必须放Q_OBJECT.但是，这样做，我得到了一个错误列表，像这样:

it seems work but not "completely". My slot doens't work. I suppose i have to put Q_OBJECT. BUT, doing so, I got a list of errors, like this:

undefined reference to `vtable for MyWidget'
........................................
collect2: error: ld returned 1 exit status
make: *** [mywidget] Error 1

我可以管理吗?问题出在哪里?

I can I manage that? Where the problem?

推荐答案

Qt中的信号和插槽通过moc:元对象编译器进行管理.基本上，moc为包含Q_OBJECT宏的每个类生成附加的C ++代码，以便有效地实现信号和时隙机制.然后，附加代码将链接到原始类声明.

Signals and slots in Qt are managed through the moc: meta object compiler. Basically, the moc generates additional C++ code for each class containing the Q_OBJECT macro in order to implement effectively the signals and slots mechanisms. The additional code is then linked to the original class declaration.

这里的问题是您的类在main.cpp中声明:这与moc如何使用您的代码冲突.您应该在单独的标题中声明您的类.

The problem here is that your class is declared in main.cpp: this conflicts with how the moc is working with your code. You should declare your class in a separate header.

有关Moc的更多信息

编辑:正如海德所指出的那样，另一种方法是在cpp中包含由moc生成的文件. 更多详细信息

as hyde pointed, an alternative is to include in your cpp the file generated by the moc; more details

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