SetProperty vs setContextProperty



  • I'm using qt quick controls 1.3. I have a working setup for communication between c++ and qml, but there are some things that I'd like to change which give me errors if I apply these changes. So I'd like to clear up a few things.

    My test program does the following: When I press a button some text appears in the text area.

    This is my class from myclass.h:
    @
    class menu_items : public QObject
    {
    Q_OBJECT
    public:
    QObject* text;
    QObject* button;

    public slots:
    void set_text ();
    };
    @

    In my main function I find pointers to QObject "text" and "button" and fill this class with them.

    This is set_text function from myclass.cpp:
    @
    void menu_items::set_text()
    {
    text->setProperty("text", "This is text!");
    }
    @

    To change text I use setProperty. To assign function to button I use setContextProperty. This is code from main.cpp:
    @
    menu_items MENU;
    QQmlContext* ctx = engine.rootContext();
    ctx->setContextProperty("menu_items", &MENU);
    @

    And this is qml code for my button:
    @
    Button
    {
    id: button1
    objectName: "button1"
    x: 550
    y: 50
    height: 25
    text: qsTr("Press Me 1")
    //onClicked: messageDialog.show(qsTr("You've pressed a button!"));
    onClicked: menu_items.set_text();
    }
    @

    This works alright, but I'd like to know why some particular changes give me errors:

    1. When assigning a function to button I have to use setContextProperty. However, I want to use setProperty instead. But if I use something like

    @button->setProperty("onClicked", &set_text());@

    Compiler fails with error:
    @c2102 & requires l-value@

    I want to use setProperty instead of setContextProperty because that way I don't have to edit qml file. In my current setup I had to specify onClicked event in qml. If it's possible, I'd like to be able fully control qml from c++ without having to edit qml.

    1. My class is in header file and class functions are in separate cpp file. I'd like to move everything to main cpp, but if I do that I get linker errors. Is header-cpp class structure mandatory for communication between qml adn c++?

    Here are error codes:
    @
    LNK2001: unresolved external symbol "public: virtual struct QMetaObject const * __thiscall menu_items::metaObject(void)const " (?metaObject@menu_items@@UBEPBUQMetaObject@@XZ)

    LNK2001: unresolved external symbol "public: virtual void * __thiscall menu_items::qt_metacast(char const *)" (?qt_metacast@menu_items@@UAEPAXPBD@Z)

    LNK2001: unresolved external symbol "public: virtual int __thiscall menu_items::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@menu_items@@UAEHW4Call@QMetaObject@@HPAPAX@Z)
    @


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