No such slot QLineEdit::setText - c++

Question

I'm trying to connect a push button to a lineEdit.when click on push button,set text of lineEdit to "Hello".
but i have a problem with signal and slot!
This is my form
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(ui->pushButton,SIGNAL(clicked()),ui->lineEdit,SLOT(setText("Hello")));
}
MainWindow::~MainWindow()
{
delete ui;
}
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QLineEdit>
#include <QPushButton>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
Application output
Starting C:\Qt\Qt5.3.0\Tools\QtCreator\bin\build-E01S01-Desktop_Qt_5_3_0_MSVC2013_OpenGL_64bit-Debug\debug\E01S01.exe...
QObject::connect: No such slot QLineEdit::setText("Hello") in ..\E01S01\mainwindow.cpp:9
QObject::connect: (sender name: 'pushButton')
QObject::connect: (receiver name: 'lineEdit')

Answer 1

You can only connect a SIGNAL to a SLOT if they has the same signature.
You can use QSignalMapper to accomplish what you want:
QSignalMapper * mapper = new QSignalMapper(this);
QObject::connect(mapper, SIGNAL(mapped(const QString&)), ui->lineEdit, SLOT(setText(const QString&)));
QObject::connect(ui->pushButton, SIGNAL(clicked()), mapper, SLOT(map()));
mapper->setMapping(ui->pushButton, tr("Hello"));

Answer 2

Since you are using Qt5, you can use a lambda expression.
First make sure c++11 is enabled by adding CONFIG += c++11 in your .pro file.
#include <QApplication>
#include <QWidget>
#include <QLayout>
#include <QLineEdit>
#include <QPushButton>
class Widget : public QWidget
{
Q_OBJECT
public:
Widget(QWidget *parent = 0) : QWidget(parent)
{
setLayout(new QVBoxLayout);
QLineEdit *lineEdit = new QLineEdit("TEXT");
QPushButton *button = new QPushButton("BUTTON");
connect(button, &QPushButton::clicked, this, [=]{lineEdit->setText("PRESSED");});
layout()->addWidget(lineEdit);
layout()->addWidget(button);
}
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Widget w;
w.show();
return a.exec();
}
#include "main.moc"