不完整类型 Qt 的无效使用

2022-01-11 00:00:00 qt linker base-class c++

我有个小问题:

finddialog.h

#ifndef FINDDIALOG_H
#define FINDDIALOG_H

class QDialog;
class QWidget;
class QLineEdit;
class QPushButton;
class QCheckBox;
class QLabel;

class FindDialog : public QDialog
{
    Q_OBJECT


public:
    FindDialog(QWidget *parent);

private slots:
    void findClicked();
    void enableFindButton(const QString &text);

signals :
    void findNext(const QString &str, Qt::CaseSensitivity cs);
    void findPrev(const QString &str, Qt::CaseSensitivity cs);

private:
    QLabel *findLabel;
    QLineEdit *textEdit;
    QCheckBox *caseCheckBox;
    QCheckBox *backwCheckBox;
    QPushButton *findButton;
    QPushButton *closeButton;

};

#endif // FINDDIALOG_H

finddialog.c

#include <QtWidgets>
#include "finddialog.h"


FindDialog::FindDialog(QWidget *parent) : QDialog(parent)
{
    QPushButton *button = new QPushButton(this);
}

void FindDialog::findClicked()
{

}

void FindDialog::enableFindButton(const QString &text)
{

}

我收到 QDialog/QPushButton 无效使用不完整类型错误.

I receive a QDialog/QPushButton invalid use of incomplete type error.

我已经在 .cpp 文件中包含了 QtWidget 为什么它不起作用?

I have already included QtWidget in .cpp file so why is it not working?

推荐答案

(Forward) 声明对于基类类型是不够的.你必须提供定义(使 QDialog 成为一个完整的类型)，所以:

(Forward) declaration is not enough for a base-class type. You have to provide the definition (make QDialog a complete type), so:

#include <QDialog>

在头文件中.请参阅基类的前向声明.

根据您发布的代码，我不知道 QPushButton 不完整的错误来自哪里(当然，如果您 #include <QtWidgets>).

Based on the code you posted, I don't know where the error about QPushButton being incomplete comes from (if you #include <QtWidgets>, of course).

如果你不 #include <QtWidgets>(其中有 #include <QPushButton> 等...)，你不能实例化任何这些不完整的类型，像这样:

If you do not #include <QtWidgets> (which has #include <QPushButton>, etc...), you cannot instantiate any of these incomplete types, like so:

new QPushButton(this);

同样，需要定义(QPushButton 需要的内存大小是多少?调用什么构造函数?只有在该编译单元中有定义时才知道 - .cpp文件).
That again, requires a definition (What's the size of the memory QPushButton needs? What constructor to call? That's known only if there's a definition in that compilation unit - .cpp file).

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