Add new TreeItemWidget using GUI of different class

[sam123]

Hello,
I want to add QTreeWidgetItem using QPussbutton and QlineEdit of different class. here is my code

mainWindow.h

#include <QMainWindow>
#include "name.h"
.
.
.
class MainWindow : public QMainWindow
{
 Q_OBJECT
 
public:
 
 void addNewItemToTree(QTreeWidgetItem *item);
 
private;
 
Ui::MainWindow *ui;
 
}

#include <QMainWindow>
#include "name.h"
.
.
.
class MainWindow : public QMainWindow
{
 Q_OBJECT

public:

 void addNewItemToTree(QTreeWidgetItem *item);

private;

Ui::MainWindow *ui;

}

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mainWindow.cpp

#include "mainwindow.h"
.
.
.
void MainWindow::addNewItemToTree(QTreeWidgetItem *item)
{
    ui->treeWidget->setColumncount(1);
    ui->treeWidget->addTopLevelItem(item);
}

#include "mainwindow.h"
.
.
.
void MainWindow::addNewItemToTree(QTreeWidgetItem *item)
{
    ui->treeWidget->setColumncount(1);
    ui->treeWidget->addTopLevelItem(item);
}

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name.h

#include <QWidget>
#include "mainwindow.h"
.
.
.
class Name : public QWidget
{
 Q_OBJECT
 
public:
 
Qstring getName(void);
 
private:
 
void on_Pussbutton_clicked();
 
UI::Name * ui;

#include <QWidget>
#include "mainwindow.h"
.
.
.
class Name : public QWidget
{
 Q_OBJECT

public:

Qstring getName(void);

private:

void on_Pussbutton_clicked();

UI::Name * ui;

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name.cpp

#include "name.h"
.
.
.
QString Name:: getName (void)
{
   return ui->lineEdit->text();
}
 
void Name::on_PussButton_clicked()
{
 
  QTreeWidgetItem *item = new QTreeWidgetItem();
  item->setText(0,getName());
 
 
   MainWindow * mainW;              // use poiter of MainWindow class
   mainW->addNewItemToTree(item);  // add New Item in the fuction of MainWindow
}

#include "name.h"
.
.
.
QString Name:: getName (void)
{
   return ui->lineEdit->text();
}

void Name::on_PussButton_clicked()
{

  QTreeWidgetItem *item = new QTreeWidgetItem();
  item->setText(0,getName());


   MainWindow * mainW;              // use poiter of MainWindow class
   mainW->addNewItemToTree(item);  // add New Item in the fuction of MainWindow
}

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(Code hab been typed so plese ignor smalls mistacks)
I am using these code. After clicking pussbutton item is not added in TreeWidget even I am not getting output either neither error.

looking for your guidance or solution..

Thanks..