How to set model data from QML?

Question

In C++ we can use QAbstractItemModel::setData() to modify the model's data. Searching the internet I only found how to read data from model to display it in a delegate. There are also some examples of adding and removing rows, but I could not find how to change the data of specific model index. Something like:

Slider {
    onValueChanged: myModel.setData(0, {amount: value})
}

How can I modify data in a model from in QML?

Answer 1

In my projects I follow a different way to read/write data from/to QML models I simply create two .qml file one to display and the another is a helper file to do database operations, and I create a model that inherits QAbstractItemModel and add four functions to it:

MyCustomObject * at(int index); // get an item to display

void reload(); // to notify QML view on update/delete

bool insert(MyCustomObject *p_myCustomObject); // insert an item in model or database

bool update(MyCustomObject *p_myCustomObject);// update an item to model or database

bool doDelete(int myCustomObjectID);// delete an item from model or database

then I create a local object to read/write, and when displaying these data I populate the local object value from the model and when I want to save I write that object to database

add this property to your main display class

property MyCustomObject myCustomObject : MyCustomObject{} // to read/write UI value ti/from it

and here is a helper class that reads UI values and insert, update or delete to/from models

Note: this class is for one of my applications, though just read it and modify it to meet your needs

import QtQuick 2.0
import DOO.Commands.Son 1.0
import DOOTypes 1.0

QtObject {

    // read ui values into local son
    function readUIValues()
    {
        var v_son =  SonFactory.createObject()
        v_son.name = sonName.text
        v_son.image = sonImage.picture
        v_son.age = sonAge.text
        v_son.entryDate = Date.fromLocaleDateString(Qt.locale(), sonEntryDate.text, "dd-MM-yyyy")
        v_son.commingFrom = sonCommingFrom.text
        v_son.disabilityKind.kind = sonDisabilityKind.currentIndex
        v_son.caseDescription = sonCaseDescription.text

        return v_son

    }
    // simple UI validation
    function validateUIValues()
    {
        if(sonName.text == "") return false
        if(sonImage.picture == "") return false
        if(sonAge.text < 1 || sonAge.text > 100) return false
        if(Date.fromLocaleDateString(Qt.locale(), sonEntryDate.text, "dd-MM-yyyy") == "Invalid Date") return false
        if(sonCommingFrom.text == "") return false
        if(sonDisabilityKind.text == "") return false
        if(sonCaseDescription.text == "") return false

        return true
    }

    // save or update a son into database
    function save()
    {

        if (!validateUIValues())
        {
            dooNotifier.showMessage("خطأ","ليدك مدخلات غير صحيحة، يُرجى التأكد من إدخال قيم صحيحة")
            return
        }

        var v_son =  readUIValues()


        if(disMode === DOO.CreateNew)
        {
            if(SonResultsModel.insert(v_son))
            {
                dooNotifier.showMessage("تم بنجاح","تم إضافة الابن بنجاح")
                sonDisplay.hide()
            }
            else
            {
                dooNotifier.showMessage("فشل","فشل إضافة الابن")
                DOOLogger.log(SonResultsModel.lasrErrorText())
            }
        }
        else
        {
            //get the ID of the son bieng edited
            v_son.sonID = son.sonID

            if(SonResultsModel.update(v_son))
            {
                dooNotifier.showMessage("تم بنجاح","تم تحديث الابن بنجاح")
                sonDisplay.hide()
            }
            else
            {
                dooNotifier.showMessage("فشل","فشل تحديث الابن")
                DOOLogger.log(SonResultsModel.lasrErrorText())
            }
        }

        v_son.destroy()
    }

    function doDelete(sonID)
    {
        if(SonResultsModel.doDelete(sonID)) {
            dooNotifier.showMessage("تم بنجاح","تم حذف الابن بنجاح")
            sonDisplay.hide()
        }
        else dooNotifier.showMessage("فشل","فشل حذف الابن")
    }
}

this is the way I use to read and write to/from databases I hope it helps