LineEdit .isEmpty() Problem

[M4RZB4Ni]

hello,
i have a lineEdit on My form and i want set a if on it
that when my lineedit are empty my pushButton set disable(true)
and when line edit are not empty my push button set disable(false)
i wrote this codes but not Worked!
what i must to do?

if(ui->lineEdit_47->text().isEmpty()){
           ui->pushButton_8->setDisabled(true);

        }else{
            ui->pushButton_8->setDisabled(false);
}

[Mitchell]

@M4RZB4Ni
The code you wrote is correct. What you need to do is make sure it is connected to a slot. The slot will call a function whenever the lineEdit gets changed and you can check to see if you need to disable or enable the button. Here is some sample code. It has a lineEdit and a button. In the constructor you will do the check to see if you need to enable or disable the button. And then when ever some one changes the text it will call a function and update the state of the button.
Hope this helps out.

mainWindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
	class MainWindow;
	}

class MainWindow : public QMainWindow
{
	Q_OBJECT

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

private slots:
	void	on_pushButton_clicked();
	void	onTextChanged(QString a_strString);

private:
	Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

mainWindow.cpp

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

#include <QSettings>
#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
	QMainWindow(parent),
	ui(new Ui::MainWindow)
{
	ui->setupUi(this);

	//set slots to see if the line edit has chanegd
	connect(ui->lineEdit,
			SIGNAL(textChanged(QString)),
			this,
			SLOT(onTextEdited(QString)));

	if(ui->lineEdit->text().isEmpty()) {
		qDebug() << "THis works";
		ui->pushButton->setDisabled(true);
	} else {
		ui->pushButton->setDisabled(false);
	}
}

MainWindow::~MainWindow()
{
	delete ui;
}

void MainWindow::on_pushButton_clicked()
{

}

void MainWindow::onTextChanged(QString a_strString)
{
	//the text has been edited so you need to see if it is empty
	if(ui->lineEdit->text().isEmpty()) {
		ui->pushButton->setDisabled(true);
	} else {
		ui->pushButton->setDisabled(false);
	}
}

[SGaist]

Hi,

A shorter version:

void MainWindow::onTextChanged(const QString &a_strString)
{
    ui->pushButton->setDisabled(a_strString.isEmpty());
}

One some small thing: use a const reference to your QString parameter, that will avoid a useless copy.

[M4RZB4Ni]

@SGaist
Thank You so much ,
My problem solved! :)