QDeclarativeListProperty add item from qml application

goli

down vote
favorite is there any why to add item to QDeclarativeListProperty from qml file at run time? in a loop, for example:

@var i;
for(i = 0 ; i < 100 ; ++i)
{
listOfItems.append(MyItem {text:"list"+i})
}@
and listOfItems is the QDeclarativeListProperty list...
i don't want to do that:
@listOfItems:
[
MyItem{text:"list val1"},
MyItem{text:"list val2"},
......
] @

i have a lot of item that should be in this list

sigrid

In order for this to work, you need to implement the "AppendFunction":http://doc.qt.nokia.com/latest/qdeclarativelistproperty.html#AppendFunction-typedef of QDeclarativeListProperty. The example below shows how that can be done. It also implement "ClearFunction":http://doc.qt.nokia.com/4.7/qdeclarativelistproperty.html#ClearFunction-typedef so that it cleans up correctly.

@
#include <QtDeclarative>

class MyObject : public QObject
{
Q_OBJECT
Q_PROPERTY(QDeclarativeListProperty<MyObject> getInfo READ getInfo CONSTANT)
public:
MyObject()
{}

~MyObject() 
{ 
} 
QDeclarativeListProperty<MyObject> getInfo() 
{ 
    for (int i = 0; i < 10; ++i) 
    { 
        list << new MyObject();

}

    return QDeclarativeListProperty<MyObject>(this, 0, &MyObject::appendObject, 0, 0, &MyObject::clearObject); 
}
static void appendObject(QDeclarativeListProperty<MyObject> *l, MyObject *obj)
{   
    MyObject *object = qobject_cast<MyObject *>(l->object);
    if (object)
        object->list << obj;
}
static void clearObject(QDeclarativeListProperty<MyObject> *l)
{
    qDebug("In clear");
    MyObject *object = qobject_cast<MyObject *>(l->object);
    if (object) {
        foreach (MyObject *o, object->list)
            delete o;
        object->list.clear();
    }
}
QList<MyObject *> list;

};
@

goli

but this way you can only add items to the list in the qml file like this:
@MyObject
{
...

getInfo :[
MyObject {...},
MyObject {...},
MyObject {...}
]
}@

i wan't to know if there is any way to add items to this list in a loop, because i have a lot of items to append into the list.

jonathanz

I have a similar requirement: Append item to an initialized list property from QML application at run-time.

This is what we can do right now, at the initialization stage:

@MyElement {
id: myElement

listOfItems: [                   
    MyItem {text: "list val1"}, 
    MyItem {text: "list val2"}

]
}@

This is what I would like to do additionally, at run time:

@myElement.listOfItems.append(MyItem {text: "list val3" });@

or:

@MyItem {
id: myItem3

 text: "list val3"

}

myElement.listOfItems.append(myItem3);
@
But neither "append()" works. This means that QDeclarativeListProperty is static once initialized in QML. This is a big limitation. Refer to the "Birthday Party" example. We have an initial list of guests. Later a new guest wants to join the fun. Will this be possible?

moldovan.catalin

This seems to be a very big limit to QDeclarativeListProperty<T*> properties. I couldn't find a way to dynamically append items to a QDeclarativeListProperty list from QML nor to dynamically create a new list and replace the old list with a new one. I can't believe that this was overlooked by Trolltech guys, it's a serious limitation if you want to do application logic with QML and Javascript, or am I missing a point here?

jonathanz

As an alternative solution, this is what I do when a dynamic list is needed: Derive a new class from QAbstractListModel and expose it to QML, or somehow make use of ListModel.

When only a static list is needed, QDeclarativeListProperty appears to be a very good choice.