Does Qt controls have a property to store data that is closely associated with the control?

[phamtv]

I am developing an application with controls that has a data structure associated to it. Is there a generic property for Qt control that I can set the data to? Something similar to VS .net´s control.Tag property.

thanks in advance!

[Guest]

The Meta-Object system and Q_PROPERTY .. something that you can use?

[phamtv]

Not quite what I am looking for. I was hoping for something like this...

// Data Associated Class
class MyObject : public QObject
{
public:
QString Name;
QString Address;
int value;

QString ToHex(int value);
QString ToBinary(int value);

}

//Main form calling function
void OnButtonClicked()
{
MyObject* obj = (MyObject*)txt_Value->Tag; // Does Qt contain something like this object

if (HexFlg)
    txt_Value.SetText(obj->ToHex((int)txt_Value->Text());
else
    txt_Value.SetText(obj->ToBinary((int)txt_Value->Text());

}

Thanks!

[Guest]

can you markup the code pls, using @ tag

[phamtv]

Sorry, I did not realize I can do the following....

@// Data Associated Class
class MyObject : public QObject
{
public: // Variables
QString Name;
QString Address;
int value;

// public methods
QString ToHex(int value); 
QString ToBinary(int value);

}

//Main form calling function
void OnButtonClicked()
{
// assign object to the control associated data (Does Qt control contain such object???)
MyObject* obj = (MyObject*)txt_Value->Tag;

if (HexFlg) 
    txt_Value.SetText(obj->ToHex((int)txt_Value->Text()); 
else 
    txt_Value.SetText(obj->ToBinary((int)txt_Value->Text());

} @

[phamtv]

bq. Sorry, I did not realize I can do the following…

I meant I did not know I can format my code in such manner. I am still curious if Qt controls contain a generic object property so I can assign my associated data to it... Sorry for any confusion.

[goetz]

What are Name and Address in MyObject for? They are not used!

What type/class is txt_Value?

Do you really want to just cast any text you get with txt_Value->Text() to an int without checking if that's possible?

From what I guess it to be, I'd extend the Qt Widget and handle the signals internally and put the computed result into a Q_PROPERTY that can read afterwards.

[Guest]

you can find more info "here":http://doc.trolltech.com/4.7-snapshot/properties.html#qt-s-property-system

[phamtv]

The code snippet is just a sample of what I would like to do. I have not added any error checking or such.

bq. What type/class is txt_Value?

txt_Value is a lineedit widget.

My main objective is to have all my widget assigned to its associated data class in the constructor so that I can cast the widget generic QObject property (if it exist) when a certain signal is received. I understand that I can create a custom class inherited from any of Qt widget and add a Q_PROPERTY that I can set. I am just wondering if Qt´s basic controls such as combobox, line edit, label, etc.. already contain this and that I have overlooked something.

[Uwe Kindler]

Each Qt widget is derived from QObject. That means you can use the @setProperty()@ function of each widget to dynamically assign any data to the widget. Later you can read out the data with the @property()@ function of the widget.

You wil find more information here "http://doc.qt.nokia.com/4.7/qobject.html#setProperty":http://doc.qt.nokia.com/4.7/qobject.html#setProperty

[phamtv]

thank you guys for your response!!! you guys were really helpful in pointing out to me that I can dynamically create a property for my widgets.

[goetz]

Some of the Qt Widgets support already associating some data with it (e.g. QComboBox can associate a QVariant value to each of the choices you have, see "http://doc.qt.nokia.com/4.7/qcombobox.html#addItem":http://doc.qt.nokia.com/4.7/qcombobox.html#addItem