#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QStandardItemModel>
#include <QDebug>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

    QStandardItemModel* model;
    QList <QStandardItem*> item;
    QList <QStandardItem*> childItem;

private slots:
    void on_pushButton_clicked();

    void on_pushButton_2_clicked();

    void on_pushButton_3_clicked();

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    model = new QStandardItemModel(this);
    ui->treeView->setModel(model);
}

MainWindow::~MainWindow()
{
    delete ui;
}
//--------добавить родителя 
void MainWindow::on_pushButton_clicked()
{

   item.append(new QStandardItem ("animals"));
    model->appendRow(item.last());
}

//-------добавить наследника
void MainWindow::on_pushButton_2_clicked()
{
    childItem.append(new QStandardItem("dog"));
    QModelIndex index = ui->treeView->selectionModel()->currentIndex();
    item[index.row()]->appendRow(childItem.last());

}

//--------удалить итем
void MainWindow::on_pushButton_3_clicked()
{
    QModelIndex index = ui->treeView->selectionModel()->currentIndex();
    model-> removeRow(index.row(),index);
    qDebug() << index;
}

QModelIndex::internalPointer()