QCompleter with additional result

Need some help. I have a QCompleter with some QStringList, for example:

QstringList list;
list << "world" << "mouse" << "user";

It works fine when user searches in QLineEdit for a word from this list, but I want to show a changed result. For example: user types world and it shows hello world in completer popup.

Is it possible? If yes - how?

First you must place the data in a model, in this case you will use QStandardItemModel, on the other hand to modify the popup you must establish a new delegate, and finally so that when you select an item to be shown in the QLineEdit you must override the pathFromIndex() method :

#include <QApplication>
#include <QCompleter>
#include <QLineEdit>
#include <QStandardItemModel>
#include <QStyledItemDelegate>
#include <QAbstractItemView>

class PopupDelegate: public QStyledItemDelegate
{
public:
    using QStyledItemDelegate::QStyledItemDelegate;
protected:
    void initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const
    {
        QStyledItemDelegate::initStyleOption(option, index);
        option->text = index.data(Qt::UserRole+1).toString();
    }
};

class CustomCompleter: public QCompleter
{
public:
    using QCompleter::QCompleter;
    QString pathFromIndex(const QModelIndex &index) const{
        return index.data(Qt::UserRole+1).toString();
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QLineEdit w;

    QStandardItemModel *model = new QStandardItemModel(&w);
    const std::vector<std::pair<QString, QString>> data{ {"London", "town London"},
                                                         {"Moscow", "town Moscow"},
                                                         {"Tokyo", "town Tokyo"}};
    for(const std::pair<QString, QString> & p: data){
        QStandardItem *item = new QStandardItem(p.first);
        item->setData(p.second, Qt::UserRole+1);
        model->appendRow(item);
    }
    CustomCompleter *completer = new CustomCompleter(&w);
    completer->setModel(model);

    PopupDelegate *delegate = new PopupDelegate(&w);
    completer->popup()->setItemDelegate(delegate);
    w.setCompleter(completer);
    w.show();

    return a.exec();
}