Is it possible to dynamically assign a component?

mzimmers

Hi all -

Is there some way to do this?

Component {
	id: loaderComponent
	Pump {} // can I assign this with a variable or property?
}

Thanks...

fcarney

"dynamically assign"
What does this mean?

mzimmers

Hi @fcarney - the snippet is from a file that gets used for many pieces of equipment: pump, filter, cleaner, etc. In my example, I'd like to replace "Pump" with a variable or something that I can pass into this file through a property.

JoeCFD

is it like you define a property string or int in Pump and replace it here?

mzimmers

@JoeCFD what I'm trying to do is eliminate the hard-coding of the Pump within the Component.

Component {
	id: loaderComponent
	Pump {} // can I use a variable instead of saying "Pump"?
}

Bob64

Have you looked at createComponent and createObject?

mzimmers

@Bob64 yes I have looked at those. I can go that route if necessary -- I just wanted to see if I was overlooking something far simpler (which I often do).

I tried this:

        Loader {
            id: drawerLoader
            active: drawer.opened
        }
        Component.onCompleted: {
            drawerLoader.setSource(tile.drawerFile,
                                   {"titleText": tile.titleText})
        }

Curiously, this loaded the file, but my argument didn't come through...

dheerendra

This is not possible. Better you can look at createQmlObject(..). You can build string dynamically & use for creation of objects.

mzimmers

Let me ask the question differently, since I still have the feeling I'm overcomplicating this.

I want a QML object that I can reuse. The object will contain a Drawer, the contents of which will be different for each instance of the object. I also need to pass arguments into the object. How best to do this?

Thanks...

JoeCFD

sounds like you need a model for qml object. The arguments can be defined or stored in the model. Different models are applied to the qml. Check XmlListModel or VisualItemModel out to see if it helps.

TomZ

@mzimmers said in Is it possible to dynamically assign a component?:

I want a QML object that I can reuse. The object will contain a Drawer, the contents of which will be different for each instance of the object. I also need to pass arguments into the object. How best to do this?

Declarative-ly.

Take a look at the 'model' property in Repeater, for instance.

If this is specifically about a Loader, you can use the 'item' property and the onLoaded callback.

Loader {
    id: foo
    onLoaded: {
        item.model = something;            
    }
}

mzimmers

@TomZ thanks for the suggestion. Are you sure your code example is correct? I tried this:

    Loader {
            id: drawerLoader
            active: drawer.opened
            source: tile.drawerFile
            onLoaded: {
                   item.model = 10;
               }
        }

And got an error: Error: Cannot assign to non-existent property "model"

TomZ

Loader takes a source property which points to your re-usable QML component. (or sourceComponent, check the docs).

The actual reusable QML component in my example is not listed. It would be the one that has a property QtObject model: null or similar, which it uses internally to 'do stuff'.

My example is thus purely meant to illustrate the way for you to assign your data to the re-usable component you would write yourself.

mzimmers

Hey everybody -

Thanks for all the good suggestions. I fill file them away for future use. For my current issue, here's how I solved it:

Rectangle {
    id: tile

    property url drawerFile: "" // supplied by caller
    property string titleText: "" // supplied by caller
    property string statusText: "" // supplied by caller

    Drawer {
        id: drawer
        
        Loader {
            id: drawerLoader
            anchors.fill: parent
            active: drawer.opened
            source: tile.drawerFile
            onLoaded: {
                item.titleText = tile.titleText
                item.statusText = tile.statusText
            }
        }
    }
}

This is what I was looking for: both the item itself (tile.drawerfile) and arguments to the item (item.titleText and item.statusText) can be expressed with variables (properties).

Thanks again...

kshegunov

I imagine what you want is something of this sort:

Item
{
    id: tile
    property alias delegate: loader.source
    property alias opened: loader.active
    property string titleText: ""
    property string statusText: ""

    Loader {
        id: loader
        anchors.fill: parent
        active: false
        onLoaded: {
            item.titleText = Qt.binding(function() { return tile.titleText })
            item.statusText = Qt.binding(function() { return tile.statusText })
        }
    }
}

You do want the property to update if/when it's changed, and also not to define properties needlessly - just alias what you can.

PS.
Or even better would be to alias sourceComponent of the Loader, not the url proper.

mzimmers

@kshegunov thanks for the suggestions. I'm curious why you think it would be better to use sourceComponent instead of source.

kshegunov

@mzimmers said in Is it possible to dynamically assign a component?:

@kshegunov thanks for the suggestions. I'm curious why you think it would be better to use sourceComponent instead of source.

It's much more flexible. I can define the component in the source of the user file (the QML that uses the above), or I can instantiate it from a QML file by name, or - god forbid ;) - expose it from C++ ...

e.g.

Component {
   id: someComponent
   ComboBox {}
}

MyTile {
   delegate: someComponent
   opened: true
   titleText: "whatever"
}