Release memory from QAbstractItemModel

[manny_lp]

Hi all,

I am using QAbstractItemModel to maintain a list in qt application. If I use
foreach (QObject *obj, _items) {
obj->deleteLater();
}
_items.clear();

whether it will release the memory ? Because in case std::vector memory remains attached to the vector after vector clear. Is it same with QAbstractItemModel?

[SGaist]

Hi,

What is _items ?
How did you create it ?

You know that even if you release memory it might not be immediately claimed by the OS ?

[eyllanesc]

@manny_lp Use qDeleteAll():

beginResetModel();
qDeleteAll(_items.begin(), _items.end());
_items.clear();
endResetModel();

[fcarney]

@eyllanesc said in Release memory from QAbstractItemModel:

qDeleteAll(_items.begin(), _items.end());

This might work too:

qDeleteAll(_items);

@manny_lp
Avoid using underscores:
https://www.gnu.org/software/libc/manual/html_node/Reserved-Names.html

[manny_lp]

@SGaist _items is list of qobjects. i.e QList<QObject *> _items;

#include "listmodel.h"
#include "qdebug.h"
using namespace models;

ListModel::ListModel(QObject *parent): QAbstractListModel(parent)
{

}

int ListModel::rowCount(const QModelIndex &parent) const
{
    return parent.isValid() ? 0 : _items.size();
}

QVariant ListModel::data(const QModelIndex &index, int role) const
{
    if ((index.row() >= 0 || index.row() < _items.count()) &&
        role == ItemRole) {
        if(index.isValid())
            return QVariant::fromValue(_items[index.row()]);
    }
    return QVariant();
}
// cppcheck-suppress unusedFunction
QHash<int, QByteArray> ListModel::roleNames() const
{
    QHash<int, QByteArray> roles;
    roles[ItemRole] = "item";
    return roles;
}

void ListModel::clearItems()
{
    foreach (QObject *obj, _items) {
        obj->deleteLater();
    }
    _items.clear();
}
#ifndef LISTMODEL_H
#define LISTMODEL_H

#include <QAbstractListModel>

namespace models
{

/**
 * @brief The ListModel class
 * Inherited from QAbstractListModel
 * Can be used by all listmodel implementations
 */
class ListModel : public QAbstractListModel
{
public:
    // User defined roles
    enum Roles
    {
        ItemRole = Qt::UserRole + 1
    };

    explicit ListModel(QObject *parent = nullptr);

    /**
     * @brief rowCount - Returns the number of rows under the given parent.
     * @param parent - QModelIndex
     * @return - int
     */
    virtual int rowCount(const QModelIndex &parent) const;
    /**
     * @brief data - Returns the data stored under the given role for the item referred to by the index.
     * @param index - index to refer. Type: QModelIndex
     * @param role - Role to access. Type: int/enum
     * @return - QVariant
     */
    virtual QVariant data(const QModelIndex &index, int role) const;
    /**
     * @brief roleNames - Returns the model's role names.
     * @return - QHash<int, QByteArray>
     */
    virtual QHash<int, QByteArray> roleNames() const;

    /**
     * @brief items - return a ref to list of items
     * @return - QList<QObject *>
     */
    const QList<QObject *> &items() const
    {
        return _items;
    }
    /**
     * @brief size - returns the size of the list
     * @return - int
     */
    int size() const
    {
        return _items.size();
    }

protected:
    // Container to hold the data
    QList<QObject *> _items;
    QList<QObject *> _emptyListToSwap;

    /**
     * @brief clearItems - Clear all the items in the list
     */
    void clearItems();
};

}

#endif // LISTMODEL_H

qDeleteAll also does not help.

[JonB]

@manny_lp said in Release memory from QAbstractItemModel:

qDeleteAll also does not help.

? What exactly is your issue? (Apart from the fact that you don't seem to actually call ListModel::clearItems())?