How i can save into JSON file a QML list model? [duplicate] - qt

Question

I am able to save settings for list items which is statically created using Component.onComponent method. But Settings for statically created list items take affect after reopening app. I would like to save settings for dynamically created list model. I am unable to save Settings for a dynamically created list item. The code below does that a list item is on and off while clicking Show/Hide action. When I reopen the app, created list item disappears. How to save list item using Setting?
import QtQuick 2.9
import Fluid.Controls 1.0
import Qt.labs.settings 1.0
import QtQuick.Controls 1.4
ApplicationWindow {
id:root
visible: true
width: 640
height: 480
property variant addlist
property int countt2: 0
Settings{
id:mysetting4
property alias ekranCosinus: root.countt2
}
function listonoff(){
if(countt2%2==1){
return true
}
else if(countt2%2==0){
return false
}
}
Connections {
target: addlist
onTriggered: listonoff()
}
addlist: favourite2
/* main.qml */
menuBar: MenuBar {
Menu {
title: "&Edit"
MenuItem { action: favourite2 }
}
}
Action {
id:favourite2
text: qsTr("Show/Hide")
onTriggered: {
countt2++
console.log(countt2)
if(listonoff()===true){
return list_model.insert(list_model.index,{ title: "First item."} )
}
else if(listonoff()===false){
return list_model.remove(list_model.index)
}
}
}
ListView {
id:contactlist
width: parent.width
height: parent.height
focus: true
interactive: true
clip: true
model: ListModel {
id:list_model
}
delegate: ListItem {
text: model.title
height:60
}
}
MouseArea {
id: mouse
anchors.fill: parent
}
}

Answer 1

Quite curious that you expect that saving a single integer value will somehow be able to store the content of an arbitrary data model... It doesn't work even for the static model data, it is only "restored" because it is static - it is part of the code, you are not really saving and restoring anything.
If you want to store all that data, you will have to serialize it when your app quits, and deserialize it when the app starts.
You could still use Settings, but to store a string value, that will represent the serialized data.
The easiest way to do it is to transfer the model items back and forth with a JS array, this way the JS JSON object functionality can be used to easily serialize and deserialize the data:
import QtQuick 2.9
import QtQuick.Controls 2.2
import QtQuick.Window 2.3
import Qt.labs.settings 1.0
ApplicationWindow {
id: main
width: 640
height: 480
visible: true
property string datastore: ""
Component.onCompleted: {
if (datastore) {
dataModel.clear()
var datamodel = JSON.parse(datastore)
for (var i = 0; i < datamodel.length; ++i) dataModel.append(datamodel[i])
}
}
onClosing: {
var datamodel = []
for (var i = 0; i < dataModel.count; ++i) datamodel.push(dataModel.get(i))
datastore = JSON.stringify(datamodel)
}
Settings {
property alias datastore: main.datastore
}
ListView {
id: view
anchors.fill: parent
model: ListModel {
id: dataModel
ListElement { name: "test1"; value: 1 }
}
delegate: Text {
text: name + " " + value
}
}
MouseArea {
anchors.fill: parent
acceptedButtons: Qt.LeftButton | Qt.RightButton
onClicked: {
if (mouse.button === Qt.LeftButton) {
var num = Math.round(Math.random() * 10)
dataModel.append({ "name": "test" + num, "value": num })
} else if (dataModel.count) {
dataModel.remove(0, 1)
}
}
}
}
The application begins with a single data model value, more data items can be added or removed by pressing the left and right mouse button respectively.
As long as the application is closed properly, the data model will be copied into an array, which will be serialized to a string, which will be stored by the Settings element. So upon relaunching the app, if the data string is present, the model is cleared to remove the initial value so it is not duplicated, the data string is deserialized back into an array, which is iterated to restore the content of the data model. Easy peasy.
Of course, you could also use the LocalStorage API as well, or even write a simple file reader and writer by exposing a C++ object to QML. All this approach needs is to be able to store and retrieve a single string.