Using a List<object> to feed a QAbstractListModel

[carpajr]

Hello!

I'm building a desktop application and want to persist some data using classes. It's just for temporary data.
I want to feed a model to delegate data inside a ListView with the class objects
The issue is I've not been able to update the model and I don't know why. Could anyone help me?

1. If I load data into the class constructor, it works. :(
2. If I try to attribute a list and emit change or use beginInsertRows, it doesn't work. :(

---

EDIT:

After 2 days of thinking about it, I decided to change lProduct as a static variable and it worked. But I know that I misunderstanding about the class scope (how I instantiate the model correctly) and it is a signal that I must back to study C++ language.

---

main.cpp

    QAbstractListModel *modelDataSession = new DataObjectModel(nullptr);
    engine.rootContext()->setContextProperty("productDataModel", modelDataSession);

dataobjectmodel.h

#ifndef DATAOBJECTMODEL_H
#define DATAOBJECTMODEL_H

#include <QObject>
#include <QAbstractListModel>

class DataObjectModel : public QAbstractListModel
{
    Q_OBJECT
    Q_ENUMS(MyRoles)
public:

    explicit DataObjectModel(QObject *parent = nullptr);

    enum MyRoles {
        ProductId = Qt::UserRole + 1,
        ProductName,
        ProductPhoto,
        ProductPrice,
        ProductQuantity
    };

    using QAbstractListModel::QAbstractListModel;

    QHash<int, QByteArray> roleNames() const override {

         qDebug() << "roleNames";

        return {
            { ProductId, "id" },
            { ProductName, "name"    },
            { ProductPhoto, "photo"  },
            { ProductPrice, "price"  },
            { ProductQuantity, "quantity" },
        };
    }

    int rowCount(const QModelIndex & parent = QModelIndex()) const override {
        qDebug() << "rowCount Updating datamodel inside data";

        if (parent.isValid()) {
            return 0;
        }
        return lProduct.size();
    }

    bool setData(const QModelIndex &index, const QVariant &value, int role) override;
    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const override;

    QList<product> getLProduct();
    void setLProduct(QList<product> &listProducts);

private:
    QList<product*> lProduct;

signals:

public slots:

    void updateModel();
};

#endif // DATAOBJECTMODEL_H

dataobjectmodel.c

#include "dataobjectmodel.h"

DataObjectModel::DataObjectModel(QObject *parent) : QAbstractListModel(parent)
{
    // this works 
    lProduct << new product(1,"nome", "photo.png", 1.45, 10);
    lProduct << new product(2,"nome 2", "photo.png", 1.9, 10);
}

bool DataObjectModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
    if (!hasIndex(index.row(), index.column(), index.parent()) || !value.isValid())
        return false;

    product item = *lProduct[index.row()];

    switch (role) {
    case ProductId:
        item.setId(value.toInt());
        break;
    case ProductName:
        item.setName(value.toString());
        break;
    case ProductPhoto:
        item.setPhoto(value.toString());
        break;
    case ProductPrice:
        item.setPrice(value.toDouble());
        break;
    case ProductQuantity:
        item.setQuantity(value.toInt());
        break;
    default:
        return false;
    }

    emit dataChanged(index, index, { role } );

    return true;
}

QVariant DataObjectModel::data(const QModelIndex &index, int role) const
{
    if (!hasIndex(index.row(), index.column(), index.parent()))
        return {};

    const product product = *lProduct[index.row()];

    switch (role) {
    case ProductId:
        return product.getId();
    case ProductName:
        return product.getName();
    case ProductPhoto:
        return product.getPhoto();
    case ProductPrice:
        return product.getPrice();
    case ProductQuantity:
        return product.getQuantity();
    default:
        return {};
    }

}


void DataObjectModel::setLProduct(QList<product> &listProducts)
{
    QList<product>::iterator i;
    lProduct.clear();
    beginInsertRows(QModelIndex(), 0, listProducts.length()-1);
    for( i= listProducts.begin(); i != listProducts.end(); i++) {
        qDebug() << "Item " << (*i).getName();
        lProduct << &(*i);
    }
     endInsertRows();

     emit dataChanged(QModelIndex(),QModelIndex());
}

[SGaist]

Hi and welcome to devnet,

@carpajr said in Using a List<object> to feed a QAbstractListModel:

product item = *lProduct[index.row()];

Looks like you are working on a copy of your object and not the original. Out of curiosity, why are you dereferencing it ?

[carpajr]

@SGaist said in Using a List<object> to feed a QAbstractListModel:

Hi and welcome to devnet,

Thank you, @SGaist !

@SGaist said in Using a List<object> to feed a QAbstractListModel:

Looks like you are working on a copy of your object and not the original. Out of curiosity, why are you dereferencing it ?

I tried everything to understand how this mechanism works. I've removed dereferencing in the variable later.

The issue seems to be here

void DataObjectModel::setLProduct(QList<product> &listProducts)
{
  // I tried before
  // lProduct = listProduct;

    QList<product>::iterator i;
    lProduct.clear();
    beginInsertRows(QModelIndex(), 0, listProducts.length()-1);
    for( i= listProducts.begin(); i != listProducts.end(); i++) {
        qDebug() << "Item " << (*i).getName();
        lProduct << (*i);
    }
     endInsertRows();

     emit dataChanged(QModelIndex(),QModelIndex());
}