Can't get access to QLineEdit - c++

Question

I'm new to QT and I've watched some tutorials about how to create a widget app. In most of them, I had to modify label text using:
ui->label->setText("smthg");
I've tried the same thing with QTextEdit and can't seem have access to it.
Tried ui->help_plz, says "no member named "textEdit" in UI::MainWindow".
How can I access QTextEdit and copy text from it?
Code:
main window.ui:
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>550</width>
<height>368</height>
</rect>
</property>
<property name="windowTitle">
<string>MainWindow</string>
</property>
<widget class="QWidget" name="centralWidget">
<widget class="QPushButton" name="pushButton">
<property name="geometry">
<rect>
<x>140</x>
<y>210</y>
<width>114</width>
<height>32</height>
</rect>
</property>
<property name="text">
<string>PushButton</string>
</property>
</widget>
<widget class="QLabel" name="succ">
<property name="geometry">
<rect>
<x>200</x>
<y>100</y>
<width>59</width>
<height>16</height>
</rect>
</property>
<property name="text">
<string>TextLabel</string>
</property>
</widget>
<widget class="QLineEdit" name="help_plz">
<property name="geometry">
<rect>
<x>230</x>
<y>60</y>
<width>113</width>
<height>21</height>
</rect>
</property>
</widget>
</widget>
<widget class="QMenuBar" name="menuBar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>550</width>
<height>22</height>
</rect>
</property>
</widget>
<widget class="QToolBar" name="mainToolBar">
<attribute name="toolBarArea">
<enum>TopToolBarArea</enum>
</attribute>
<attribute name="toolBarBreak">
<bool>false</bool>
</attribute>
</widget>
<widget class="QStatusBar" name="statusBar"/>
</widget>
<layoutdefault spacing="6" margin="11"/>
<resources/>
<connections/>
</ui>
main.cpp:
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
mainwidow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QTextEdit>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
ui->succ->setText("yeah");
ui->help_plz //no member named "help_plz" in UI::MainWindow
}
main.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = nullptr);
~MainWindow();
private slots:
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

Answer 1

It says no member named "textEdit" in UI::MainWindow because there isn't anything called textEdit in your .ui file (you can search it yourself to confirm it). You cannot access UI elements that are not there. Add a line edit to your ui file.

Answer 2

QMainWindows can be tricky. You need to set your central widget explicitly:
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
setCentralWidget(ui->centralWidget);
}
void MainWindow::on_pushButton_clicked()
{
ui->succ->setText("yeah");
ui->help_plz->setText("xxx"); //no member named "help_plz" in UI::MainWindow
}
This should compile (though I doubt it does what you want). FWIW: note that this exercise would have been more straightforward had you used QWidget instead of QMainWindow as your UI.