Qt/C++ - Lesson 001. QLineEdit IP Address

ip адрес, lineedit, ip address, qtcreator, QLineEdit IP Address, qt, QLineEdit example, qlineedit

Available similar articles in Qt/QML and PyQt5/Python

When you will develop network applications, you may need to create form for input ip-address, but the use of a simple method setInputMask("000.000.000.000;_"); of QLineEdit does not provide the proper result as this mask allows to enter the values of 999, 657, etc., while the IP-address of the limited number of 255.

One way to solve this problem is to use Validator .

Project structure

The project is created as an application Qt Widgets, where files are created by default:

• QLineEdit_IP_Address.pro - project profile;
• mainwindow.h - header file of main window;
• mainwindow.cpp - source code of main window;
• main.cpp - the main source file from which the application starts;
• mainwindow.ui - file of user interface.

Note. Most of the interface is created in the designer, so as not to clutter up the main logic code superfluous information..

mainwindow.ui

Form for QLineEdit

In the designer need to create form of window with view as on the picture.

The interest is in the form only QLineEdit , which is named lineEdit .

lineEdit.pro

This file is not interested for us, because it was created by default.

#-------------------------------------------------
#
# Project created by QtCreator 2015-08-10T14:35:22
#
#-------------------------------------------------
 
QT       += core gui
 
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
 
TARGET = lineEdit
TEMPLATE = app
 
 
SOURCES += main.cpp\
        mainwindow.cpp
 
HEADERS  += mainwindow.h
 
FORMS    += mainwindow.ui

main.cpp

This file is not interested also, it was created by default.

#include "mainwindow.h"
#include <QApplication>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
 
    return a.exec();
}

mainwindow.h

This file is not interested also, it was created by default.

#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:
    Ui::MainWindow *ui;
};
 
#endif // MAINWINDOW_H

mainwindow.cpp

In this file to create a Validator have been applied:

• QRegExp - class of regular expressions;
• QRegExpValidator - class of Validator for regular expression;

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    /* Create a string for a regular expression */
    QString ipRange = "(?:[0-1]?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])";
    /* Create a regular expression with a string 
     * as a repeating element
     */
    QRegExp ipRegex ("^" + ipRange
                     + "\\." + ipRange
                     + "\\." + ipRange
                     + "\\." + ipRange + "$");
    /* Create a validation regular expression
     * using a regular expression
     */
    QRegExpValidator *ipValidator = new QRegExpValidator(ipRegex, this);
    /* Set Validator on QLineEdit */
    ui->lineEdit->setValidator(ipValidator);
}
 
MainWindow::~MainWindow()
{
    delete ui;
}

Result

QLineEdit with ip-address validation

After creating the project you can check the work of Validator with IP-address input.