why insert one row and display tow rows, with an additional blank row?

hello everyone,

yesterday, i wrote a test programe using QTableView. i define class CustomModel inheriting from QAbstractTableModel , which implemented rowCount, columnCount, data and headerData. the CustomModel has a member customs storing the data, its a QList. i add a button to add one item to the data.

But when i click the button, the view shows tow columns, one is the item i add, the other is a blank row.

i can't solve it, thanks for your help!

its the initial state
Attachment 11699

when i click once
Attachment 11698

when i click twice
Attachment 11700

CustomModel definition

Code:

struct Custom{
    Custom();
    QString col1;
    QString col2;
    QString col3;
    QString col4;
};
 
class CustomModel : public QAbstractTableModel{
    Q_OBJECT
public:
    CustomModel(QObject* parent = 0);
    ~CustomModel();
    int rowCount(const QModelIndex &parent) const;
    int columnCount(const QModelIndex &parent) const;
    QVariant data(const QModelIndex &index, int role) const;
    QVariant headerData(int section, Qt::Orientation orientation, int role) const;
    bool appendCustom(Custom* custom, const QModelIndex &parent = QModelIndex());
private:
    QList<Custom*> customs;
};

CustomModel::appendCustom

Code:

bool CustomModel::appendCustom(Custom *custom, const QModelIndex &parent)
{
    beginInsertRows(parent, customs.count(), customs.count()+1);
    customs.append(custom);
    endInsertRows();
    return true;
}

MainWindow

Code:

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    model = new CustomModel(this);
    ui->tableView->setModel(model);
 
    connect(ui->actionAddItem, &QAction::triggered, this, &MainWindow::onAddCustom);
}

onAddCustom

Code:

void MainWindow::onAddCustom()
{
    Custom* new_custom = new Custom();
 
    model->appendCustom(new_custom);
}