Qt C++: Methods, Examples, Installation

What is this library and why is it needed

Qt is a powerful cross-platform framework for developing applications in C++. It allows you to create graphical user interfaces (GUI), console utilities, network applications, multimedia programs, and much more. Qt abstracts the developer from operating system specifics, providing a unified API for Windows, macOS, Linux, Android, and iOS.

Why is Qt needed?

Cross-platform: One code works on different OSes without changes.
Rich ecosystem: Includes modules for working with databases (Qt SQL), networking (Qt Network), web engines (Qt WebEngine), multimedia (Qt Multimedia), 3D graphics (Qt 3D), etc.
Performance: Written in C++, ensuring high execution speed.
Signal-slot system: A unique mechanism for connecting objects and handling events.
Ready-made widgets: Buttons, tables, trees, text editors, dialogs, and much more.
Development tools: Qt Creator — IDE with a visual form editor.

Qt is used in projects such as KDE (Linux desktop environment), Telegram Desktop, VirtualBox, Autodesk Maya, VLC Media Player, and many others.

Installation

Unlike interpreted languages (Python, JavaScript), Qt for C++ is not installed via pip install or npm install. It is a native library that requires compilation and project setup.

Method 1: Installation via the official installer (recommended)

Go to the official Qt website.
Download the Qt Online Installer for your OS.
Run the installer and log in to your account (or create a free one).
Select the Qt version (e.g., Qt 6.5.3) and components:
- Qt (Desktop) — for desktop applications.
- Qt Creator — IDE.
- Compilers (MinGW for Windows, GCC/Clang for Linux/macOS).
Complete the installation.

Method 2: Installation via package managers (Linux/macOS)

Ubuntu/Debian:

sudo apt updatesudo apt install qt6-base-dev qt6-tools-dev qtcreator

macOS (Homebrew):

brew install qt@6brew install qt-creator

Windows (vcpkg):

vcpkg install qt6

Method 3: CMake + FetchContent (for projects)

If you use CMake, you can automatically download Qt:

include(FetchContent)FetchContent_Declare(qt6    GIT_REPOSITORY https://github.com/qt/qt6.git    GIT_TAG v6.5.3)FetchContent_MakeAvailable(qt6)

Quick start with a code example

Let's create a simple window with a button that closes the application.

Step 1: Create the file `main.cpp`

#include <QApplication>#include <QPushButton>

int main(int argc, char *argv[]) {    QApplication app(argc, argv);

    QPushButton button("Close application");    button.resize(200, 100);    button.show();

    // Connect the button's clicked() signal to the application's quit() slot    QObject::connect(&button, &QPushButton::clicked, &app, &QApplication::quit);

    return app.exec();}

Step 2: Create the file `CMakeLists.txt`

cmake_minimum_required(VERSION 3.16)project(MyFirstQtApp)

set(CMAKE_CXX_STANDARD 17)set(CMAKE_AUTOMOC ON)

find_package(Qt6 REQUIRED COMPONENTS Widgets)

add_executable(MyFirstQtApp main.cpp)

target_link_libraries(MyFirstQtApp Qt6::Widgets)