Q_PROPERTY

[Gunkut]

Hello I want to use a variable from .qml file in a .cpp file. I want to do something according to value of (which is in .qml file) isCamRezistans in C++. So I want to put it's value into m_isCamRezistans. For that I use Q_PROPERTY as follows:

class CAN : public QObject
{
   Q_OBJECT

public:
   Q_PROPERTY(quint32 bitrate MEMBER m_bitrate WRITE setBitrate NOTIFY bitrateChanged)
   Q_PROPERTY(bool isCamRezistans MEMBER m_isCamRezistans READ m_isCamRezistans)

private:
   quint32 bitrate;
   bool m_isCamRezistans

Q_PROPERTY(quint32 bitrate MEMBER m_bitrate WRITE setBitrate NOTIFY bitrateChanged) does not give any errors. However, Q_PROPERTY(bool isCamRezistans MEMBER m_isCamRezistans READ m_isCamRezistans)
gives "error: expression cannot be used as a function." How can I solve that? Also do I need to use NOTIFY and signal slot mechanism in here? Or once I use Q_PROPERTY and READ, will the value be automatically updated?

[jsulm]

@Gunkut said in Q_PROPERTY:

READ m_isCamRezistans

READ requires a function not a variable, see https://doc.qt.io/qt-5/properties.html

[Gunkut]

Okay so is there an easier way to get values of qml variables. Because I will have many variables and writing a function for each of them looks inefficient.

[J.Hilk]

@Gunkut

Because I will have many variables and writing a function for each of them looks inefficient

Assuming you use QtCreator:

• Right mouse click on Q_PROPERTY
• Select Refactor
• Select Generate Missing Q_PROPERTY Members

[jsulm]

@Gunkut From the documentation I linked: "A READ accessor function is required if no MEMBER variable was specified". So, you don't have to provide READ at all.

[Gunkut]

@jsulm I see in that case can I only use MEMBER and not NOTIFY? Would a change in qml variable directly change the member variable? Such as using:

Q_PROPERTY(QString text MEMBER m_text )

instead of :

Q_PROPERTY(QString text MEMBER m_text NOTIFY textChanged)