[Qt-qml] Dynamically created items and properties

[Martin Jones]

On Mon, 26 Jul 2010 05:41:34 pm ext Jan Ekholm wrote:
> I tried to change the Unit item to really, really bind to the C++
> properties
> 
> using this change:
> > Item {
> > 
> >     function createUnits (component) {
> >     
> >         if ( component.status == Component.Ready ) {
> >         
> >             // get all units, this is a C++ list of Unit*
> >             var unit_list = scenario.units.units;
> >             
> >             for ( var index = 0; index < unit_list.length; index++ ) {
> >             
> >                 // the c++ unit, a Unit*
> >                 var unit = unit_list[index]
> >                 
> >                 // create a new item with the root Item as parent, see
> >                 // the "id" property
> >                 var item = component.createObject( units );
> >                 
> >                 if (item == null) {
> >                 
> >                     console.log( "Units.createUnits: failed to create
> >                     unit"
> > 
> > ); }
> > 
> >                 else {
> 
>                       item.setup( index )
> 
> >                 }
> >             
> >             }
> >         
> >         }
> >         
> >         else if (component.status == Component.Error) {
> >         
> >             // ugh
> >         
> >         }
> >     
> >     }
> >     
> >     function loadComponent () {
> >     
> >         // load the component
> >         var component = Qt.createComponent("Unit.qml");
> >         
> >         // create the real items
> >         createUnits( component );
> >     
> >     }
> >     
> >     Component.onCompleted: loadComponent();
> >     id: units
> > 
> > }
> 
> And the Unit.qml file would have this function to perform the binding:
> 
> Image {
> 
>     function setup (index) {
>             x       = scenario.units.units[index].x
>             y       = scenario.units.units[index].y
>             source  = scenario.units.units[index].icon
>             unit_id = scenario.units.units[index].id
>     }
> 
>     property int unit_id
>     ...
> }

The above is not a binding.  It is an assignment.  Bindings are created using 
the colon syntax.

One solution is to provide the Unit to the QML item and let it setup the 
bindings:

Unit.qml:

Image {
    property variant unit
    x: unit.x * 48 + ( unit.y % 2 ) * 24
    y: unit.y*36
    source: unit.icon
    unit_id: unit.id
}

Then you just need to assign the unit to the QML item and it will take care of 
its bindings.

-- 
Martin