Can't use slots in connect qt - c++

Question

When I run my project I can't use train_button to add lines in text. Because of I got this error:
QObject::connect: No such slot QTextEdit::onClick()
I try to solve it, but searched only information about adding Q_OBJECT, but I got this. My project is standart Qt Widget Application.
.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QPushButton>
#include <QTextEdit>
#include <QString>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void onClick(){
text->append("first\nsecond");
}
private:
QPushButton *train_button;
QTextEdit *text;
Ui::MainWindow *ui;
//QString a = "sdfsdfsdfsdf";
};
# endif // MAINWINDOW_H
.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow){
ui->setupUi(this);
this->setFixedSize(800,600);
text = new QTextEdit(this);
train_button = new QPushButton(this);
text->setGeometry(50,50,500,500);
text->setPlaceholderText("Here we go ...");
train_button->setText("example");
train_button->setGeometry(600,50,100,50);
train_button->setStyleSheet( "background-color: rgb(0, 255, 0);border-style: inset;border-width: 0px;border-radius: 5px;border-color: beige;font: bold 14px;min-width: 10em; padding: 2px;" );
connect(train_button,SIGNAL(clicked()),text,SLOT(onClick();));
}
MainWindow::~MainWindow()
{
delete train_button;
delete solver_button;
delete text;
delete ui;
}
I use QMake version 3.0 using Qt version 5.2.1.

Answer 1

The error is quite clear:
No such slot QTextEdit::onClick()
The documentation is clear as well. QTextEdit has no onClick slot anywhere.
It's not clear what you're trying to do. In any case, you aren't doing it correctly: you cannot connect an inexistent slot to a signal.
By looking at your code, I see that you defined onClick as a member function of MainWindow.
Therefore probably this is what you want:
connect(train_button, &QPushButton::clicked, this, &MainWindow::onClick);
That is, probably you want to attach a slot of the class MainWindow to the button, not a slot of a QTextEdit.