錯誤：變量'QQmlComponent組件'具有初始值設定項，但在Qt5中不完整類型

Question

我正在根據此導師http://qt-project.org/doc/qt-5.0/qtqml/qtqml-cppintegration-exposecppattributes.html在Qt5中向CML公開C++類型的屬性。當我運行它我得到這個錯誤在我的問題窗格錯誤：變量'QQmlComponent組件'具有初始值設定項，但不完整的類型不僅我有這個錯誤我也有這個錯誤信號我創建使用Q_PROPERTY未檢測到

C:\Users\Tekme\Documents\QtStuf\quick\QmlCpp\message.h:15: error: 'authorChanged' was not declared in this scope emit authorChanged(); ^

我的代碼是

#ifndef MESSAGE_H 
#define MESSAGE_H 
#include <QObject> 
class Message : public QObject 
{ 
Q_OBJECT 
Q_PROPERTY(QString author READ author WRITE setAuthor NOTIFY authorChanged) 
public: 
    void setAuthor(const QString &a) { 
     if (a != m_author) { 
      m_author = a; 
      emit authorChanged(); 
     } 
    } 
    QString author() const { 
     return m_author; 
    } 
private: 
    QString m_author; 
}; 
#endif 

，並在我的main.cpp

#include "message.h" 
#include <QApplication> 
#include <QQmlEngine> 
#include <QQmlContext> 
int main(int argc, char *argv[]) 
{ 
    QApplication a(argc, argv); 
    QQmlEngine engine; 
    Message msg; 
    engine.rootContext()->setContextProperty("msg",&msg); 
    QQmlComponent component(&engine, QUrl::fromLocalFile("main.qml")); 
    component.create(); 

    return a.exec(); 
} 

Answer 1

您還沒有包括QQmlComponent頭在你的main.cpp：

#include <QQmlComponent> 

您還試圖發出你還沒有宣佈的信號。你應該聲明它在你的message.h這樣的：

signals: 
    void authorChanged(); 

檢查this example。

Answer 2

我相信你需要添加：

signals: 
    void authorChanged(); 

到類像這樣：

class Message : public QObject 
{ 
Q_OBJECT 
Q_PROPERTY(QString author READ author WRITE setAuthor NOTIFY authorChanged) 
public: 
    void setAuthor(const QString &a) { 
     if (a != m_author) { 
      m_author = a; 
      emit authorChanged(); 
     } 
    } 
    QString author() const { 
     return m_author; 
    } 
signals: 
    void authorChanged(); 
private: 
    QString m_author; 
};