[Interest] Updating a model re-add everything in QML. How can i prevent that?

[Mark]

On Thu, Nov 8, 2012 at 9:55 PM, Nicolás Ulrich <nikolaseu at gmail.com> wrote:
> I got this and it seems to work fine (Qt 4.8), but it's not a model. I
> remember a similar problem with the constructor but I think it was
> because I was using Q_DECLARE_METATYPE(MyClass) instead of
> Q_DECLARE_METATYPE(MyClass*).
>
> ------------------------------
> MyClass.h
> ------------------------------
> #ifndef MYCLASS_H
> #define MYCLASS_H
>
> #include <QObject>
> #include <QVariant> // needed for Q_DECLARE_METATYPE
>
> class MyClass : public QObject
> {
>     Q_OBJECT
> public:
>     explicit MyClass(QObject *parent = 0);
>     ~MyClass();
>
> signals:
>
> public slots:
>
> private:
>
> };
> Q_DECLARE_METATYPE(MyClass*)
> #endif // MYCLASS_H
>
>
> ----------------------------------------
> main.cpp
> ----------------------------------------
> #include <QtDeclarative> // needed for qmlRegisterType
>
> int main(int argc, char** argv)
> {
>     QApplication app(argc, argv);
>     qmlRegisterType<MyClass>("MyClass", 1, 0, "MyClass");
>     ...
>
> -----------------------------
> QML
> -----------------------------
>
> import MyClass 1.0
>
>     ...
>     MyClass {}
>
>
>
>
>
> On Thu, Nov 8, 2012 at 3:09 PM, Mark <markg85 at gmail.com> wrote:
>> On Thu, Nov 8, 2012 at 6:43 PM, Nicolás Ulrich <nikolaseu at gmail.com> wrote:
>>> Are you really using this?
>>> qRegisterMetaType<PathModel*>("PathModel*");            (with the * in
>>> the string)
>>>
>>> I guess it should be
>>> qRegisterMetaType<PathModel*>("PathModel");
>>>
>>>
>>>
>>> On Thu, Nov 8, 2012 at 10:36 AM, Mark <markg85 at gmail.com> wrote:
>>>> On Thu, Nov 8, 2012 at 10:34 AM, Bo Thorsen <bo at fioniasoftware.dk> wrote:
>>>>> Den 08-11-2012 01:33, Mark skrev:
>>>>>> Hi,
>>>>>>
>>>>>> I have a models in C++ (a QStringList actually). In QML i'm displaying
>>>>>> it using a repeater. Now when i remove some items from the end of the
>>>>>> list (which happens quite a few times) then the entire list seems to
>>>>>> go through the QML repeater again.
>>>>>>
>>>>>> What i want to do is put a QStringList in a QML Repeater (works), but
>>>>>> when i remove items from the end i would like QML to be "smart" and
>>>>>> also remove the items from the end and leave those that haven't
>>>>>> changed. Thus not re-inserting all the items in the repeater when not
>>>>>> needed.
>>>>>>
>>>>>> Is there some option to get that?
>>>>>
>>>>> To do this you need a better model than a QStringList in Repeater. Take
>>>>> a look at QStringListModel instead. But if you just call setStringList()
>>>>> you won't see any improvement. You have to use insertRows and removeRows
>>>>> instead.
>>>>>
>>>>> Bo Thorsen.
>>>>>
>>>>> Come by my DevDays talk in Berlin - "Designing for testability". Learn how to build and run your unit tests with the Qt application.
>>>>>
>>>>> Fionia Software - Qt experts for hire.
>>>>>
>>>>> _______________________________________________
>>>>> Interest mailing list
>>>>> Interest at qt-project.org
>>>>> http://lists.qt-project.org/mailman/listinfo/interest
>>>>
>>>> Thanks a lot for that, that will probably work.
>>>> However, i'm hitting another issue when trying to make a custom
>>>> StringListModel (only due to setRoleNames...) This is how it looks:
>>>>
>>>> // pathmodel.h
>>>> #ifndef PATHMODEL_H
>>>> #define PATHMODEL_H
>>>>
>>>> #include <QStringListModel>
>>>>
>>>> class PathModel : public QStringListModel
>>>> {
>>>> public:
>>>>     PathModel();
>>>> };
>>>>
>>>> Q_DECLARE_METATYPE(PathModel*)
>>>>
>>>> #endif // PATHMODEL_H
>>>>
>>>>
>>>> // pathmodel.cpp
>>>> #include "pathmodel.h"
>>>>
>>>> PathModel::PathModel()
>>>> {
>>>>     QHash<int,QByteArray> roleNames;
>>>>     roleNames.insert(Qt::DisplayRole, "modelData");
>>>>     setRoleNames(roleNames);
>>>> }
>>>>
>>>> Now if i want to register the new meta type using:
>>>> qRegisterMetaType<PathModel*>("PathModel*");
>>>>
>>>> The app instantly crashes when i run it.. It must be something very
>>>> obvious that i'm missing, but i don't see it.
>>>>
>>>> Any idea what i'm doing wrong?
>>>> _______________________________________________
>>>> Interest mailing list
>>>> Interest at qt-project.org
>>>> http://lists.qt-project.org/mailman/listinfo/interest
>>
>> Yes.
>>
>> But even if i change it to your suggestion it doesn't work. It's all
>> in the private copy ctor...

Hi,

Thank you for the attempt, but models really are a different beast and
not comparable to making a QML Component (like you just did).
Right now i'm "solving" it by sending my model to QML directly using
setContextProperty but that's not what i want to do..