A problem about dynamic object management in QML, Please help me!

open-src

Hi, guys.
I used the js functions method, which the QML API Documents introduces, to create a ListView object and a ListViewDelegate object dynamically. But QtCreator complain about:
file:///media/....../componentCreation.js:65: ReferenceError: Can't find variable: pathName

@var newListViewDelegateComponent
var newListViewDelegate

var newListViewComponent
var newListView

function createSingleViewObjects(currentIndex) {
newListViewComponent = Qt.createComponent("PictureListView.qml");
newListView = newListViewComponent.createObject(qmlEvolutionWindow);

 newListViewDelegateComponent = Qt.createComponent("PictureListViewDelegate.qml");
 newListViewDelegate = newListViewDelegateComponent.createObject(qmlEvolutionWindow);



 if(newListView === null){
     console.log("Error creating new album dialog object.");
 }else{
    newListView.width = qmlEvolutionWindow.width
    newListView.height = qmlEvolutionWindow.height
    newListView.model = pictureModel
    newListView.delegate = newListViewComponent
    newListView.positionViewAtIndex(currentIndex, ListView.Center)
     newListView.z = 1

if(newListViewDelegate === null){
console.log("Error creating new album dialog object.");
}else{
newListViewDelegate.width = newListView.width
newListViewDelegate.height = newListView.height
newListViewDelegate.width = newListView.width
newListViewDelegate.height = newListView.height
newListViewDelegate.source = pathName
}

}@

There is an error in the line newListViewDelegate.source = pathName.

The "pathName" is a role in the pictureModel which is exposed from C++, and it can't assign to newListViewDelegate.source; but it seems that the pictureModel can be assigned to the newListView.model。 Any advice will be appreciated.

DenisKormalev

You can't do it. pictureName is accessable only in delegate, not outside it. If you want to dynamically change role that delegate should use you can pass role name as string (i.e. "pathName") to some delegate property (let's call it sourcePropertyName) and use it in your delegate as
@
source: eval(sourcePropertyName)
@

open-src

#Denis Kormalev
Thank you for your reply...

mmm... it's a good idea, but it seems it doesn't work in my ps file, and the other errors appear now.

What I want to do is: dynamically create a ListView object and its ListViewDelegate object using js function, but I try it two days, and always fail. I feel depressed about it, can you give me some guidance?

here is the PictureListView.qml:

@import Qt 4.7

ListView {
anchors.fill: parent

orientation: ListView.Horizontal
keyNavigationWraps:true
snapMode: ListView.SnapOneItem;
focus:true

}
@

Here is PictureListViewDelegate.qml:
@Rectangle{

property alias sourceProperty: listViewPicture.sourceString

Image{
    id:listViewPicture

    property  string  sourceString : ""

    state: "singleView"
    fillMode: Image.Stretch
    source: eval&#40;sourceString&#41;
    anchors.fill: parent
    smooth: true
    opacity: 1

}
}
@
Here is the js file used to dynamically create a ListView object and its ListViewDelegate object:
@var newListViewDelegateComponent
var newListViewDelegate

var newListViewComponent
var newListView

function createSingleViewObjects(currentIndex) {
newListViewComponent = Qt.createComponent("PictureListView.qml")
newListView = newListViewComponent.createObject(appWindow);

newListViewDelegateComponent = Qt.createComponent("PictureListViewDelegate.qml");
newListViewDelegate = newListViewDelegateComponent.createObject(appWindow);

if(newListViewDelegate === null){
    console.log("Error creating new album dialog object delegate.");
}else{
    newListViewDelegate.width = newListView.width
    newListViewDelegate.height = newListView.height
    newListViewDelegate.sourceProperty = "pathName"
    console.log(newListViewDelegate.source)
}

if(newListView === null){
    console.log("Error creating new album dialog object.");
}else{
    newListView.width = qmlEvolutionWindow.width
    newListView.height = qmlEvolutionWindow.height
    newListView.model = pictureModel
    console.log("list view's picture model has been created.")
    newListView.delegate = newListViewDelegateComponent
    newListView.positionViewAtIndex(currentIndex, ListView.Center)
    console.log("currentIndex is:");
    console.log(currentIndex);
    newListView.z = 1
}

}
@

Here is the main.qml:
@import Qt 4.7
import "../../componentCreation.js" as ComponentCreationScript

Rectangle {
id:appWindow
......
signal switchToSingleView(int currentIndex)
onSwitchToSingleView: {ComponentCreationScript.createSingleViewObjects(currentIndex)}
......
}
@

QtCreator complain about an error:
file:///media/....../qml/qml_evolution/PictureListViewDelegate.qml:14: Unable to assign [undefined] to QUrl source
<Unknown File>:1: ReferenceError: Can't find variable: pathName
undefined

The content of that line is ：
source: eval(sourceString)

DenisKormalev

It will not work. Why do you create object of your delegate in js code? New delegate objects will be created by view. You should implement some mechanism of passing name of needed property. For example you can always use some role name for it (in all your models).