Dynamically bind values from qml to repeater created object - qt

Question

I control the position of some elements of my scene using alias properties likes this : If I have a file Foo.qml containing
Item {
property alias myprop1: id1
property alias myprop2: id2
Node {id:id1,...}
Node {id:id2,...}
On my main, I can then call
Slider{
id:myslider
}
foo{
myprop1.x: myslider.value
}
Now if my Foo.qml contains an unknow number of properties (lets say they are all called mypropX). If I have 10 properties I want to create 10 sliders, one for each property. It is possible with a repeater and loop like mentioned in last answer here
Foo{
id:myfoo
}
Column {
Repeater {
id: myrepeater
delegate: Slider {
from:0
to:400
y: 12*index
}
Component.onCompleted: {
let propArray = [];
for(var prop in myfoo){
//select only the properties I'm interested in
//a "onXXXChanged" is created on each properties so I also have to remove it
if(prop.substring(0, 6)==="myprop" && prop.substring(prop.length-7,prop.length)!=="Changed"){
propArray.push(prop)
}
}
myrepeater.model = propArray
}
}
}
The problem is now that I don't know how to bind those 10 sliders to my properties.
I tried adding to my Foo instance in main
Component.onCompleted: {
let i=0
for(var prop in myfoo){
if(prop.substring(0, 6)==="myprop" && prop.substring(prop.length-7,prop.length)!=="Changed"){
//equivalent to myprop1.x: myslider.value when there was no repeater
myfoo.prop.x = Qt.binding(function() {
return myrepeater.itemAt(i).value
})
i++
}
}
}
But it return
QQmlEngine::setContextForObject(): Object already has a QQmlContext
qrc:/main.qml:145: Error: Cannot assign to non-existent property "prop"
The problem is that in the for loop, prop is a string. I am also not sure that at the moment the onCompleted is executed, the repeater has already created all the slidders.
I could use the QML type Bindings{} which takes a target (myrepeater.itemAt(i).value) and the property name as a string, but I don't know how to call the Bindings{} type from javascript

Answer 1

You can use the [] operator to read the properties from myfoo and as discussed I would use a Binding object inside the delegate:
import QtQuick 2.11
import QtQuick.Window 2.11
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3
Window {
width: 640
height: 480
visible: true
title: qsTr("Hello World")
Item {
id: myfoo
property int myprop_upper_threshold
onMyprop_upper_thresholdChanged: console.log("upper_threshold", myprop_upper_threshold)
property int myprop_lower_threshold
onMyprop_lower_thresholdChanged: console.log("lower_threshold", myprop_lower_threshold)
}
ColumnLayout {
Repeater {
id: myrepeater
delegate: Slider {
id: myslider
from: 0
to: 400
Text {
text: modelData
}
Binding {
target: myfoo
property: modelData
value: myslider.value
}
}
Component.onCompleted: {
let propArray = [];
for(var prop in myfoo)
{
//select only the properties I'm interested in
//a "onXXXChanged" is created on each properties so I also have to remove it
if(prop.substring(0, 6)==="myprop" && prop.substring(prop.length-7,prop.length)!=="Changed")
{
propArray.push(prop)
}
}
myrepeater.model = propArray
}
}
}
}