error: variable 'QQmlComponent component' has initializer but incomplete type in Qt5

Question

i am playing with Exposing Attributes of C++ Types to QML in Qt5 based on this tutor http://qt-project.org/doc/qt-5.0/qtqml/qtqml-cppintegration-exposecppattributes.html. when i

Answer 1

You are not including QQmlComponent header in your main.cpp:

#include <QQmlComponent>

You are also trying to emit a signal that you haven't declared yet. You should declare it in your message.h like this:

signals:
    void authorChanged();

Check this example.

Answer 2

I believe you need to add:

signals: 
  void authorChanged();

to your class like this:

  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;
};