QML: memory problem

Nunnito

Hello!
I am very new to QML, sorry if my question is a bit silly.

I would like to know the reason why when I destroy an item that takes a lot of memory, this item does not free the memory.

Example:

import QtQuick 2.15
import QtQuick.Controls 2.15

ApplicationWindow {
    visible: true; width: 750; height: 750
    Button {
        y: 250
        text: "More"
        onClicked: repeater.model += 5000
    }
    Button {
        y: 500
        text: "Less"
        onClicked: repeater.destroy()
    }
    Row{
        Repeater {
            id: repeater
            model: 0
            Button {}
        }
    }
}

In the code, when I press the "More" button, about 250MB is stored in memory.
And when I press the "Less" button, the repeater is destroyed, but QML does not release the memory that the repeater was taking.

I would like to know the reason for this.
Thanks for your time!

ODБOï

@Nunnito hi and welcome
Please read the warnings here : https://doc.qt.io/qt-5/qtqml-javascript-dynamicobjectcreation.html#deleting-objects-dynamically

Nunnito

Hi, thanks for the answer.

I created the following code using Qt.createComponent():

import QtQuick 2.15
import QtQuick.Controls 2.15

ApplicationWindow {
    visible: true; width: 250; height: 250

    Button {
        y: 125
        text: "Destroy"
        onClicked: {
            for (var i = 0; i < row.children.length; i++) {
                row.children[i].destroy()
            }
        }
    }

    Row {
        id: row
    }

    Component.onCompleted: {
        var component = Qt.createComponent("MakeButton.qml")

        for (var i = 0; i < 5000; i++){
            component.createObject(row)
        }
    }
}

And the problem persists, the memory is not freed.

Is something wrong with the code?

ODБOï

@Nunnito apparently QML keeps the memory for future usage as you can reed here or here
you can test it my creating and deleting objects several times, you will see the memory consumption will stay stable

    Row{
        Button {
            y: 125
            text: "Create"
            onClicked: {
                var component = Qt.createComponent("MakeButton.qml")
                for (var i = 0; i < 2000; i++){
                    component.createObject(row)
                }
            }
        }

        Button {
            y: 125
            text: "Destroy"
            onClicked: {
                for (var i = 0; i < row.children.length; i++) {
                    row.children[i].destroy()
                }
            }
        }
    }

    Row {
        id: row
    }

https://blog.basyskom.com/qtws15-a-deep-dive-into-qml-memory-management-internals/ this is a bit old thought but still very interesting