Warsztaty z QT

O ile dobrze pójdzie to przyda się nam poniższy kod:

	#include <QFile>
	#include <QPixmap>
	#include <QSqlDatabase>
	#include <QSqlRecord>
	#include <QSqlError>
	#include <QSqlQuery>
	#include <QDebug>
	#include "studentdbhandler.h"
	void StudentDBHandler::createTableIfNotExists(QSqlDatabase &db)
	{
	if (!db.isOpen()) {
	qDebug() << "Error: Failed to connect to database";
	return;
	}
	QSqlQuery query(db);
	QString createTableQuery;
	if ("QSQLITE" == m_dbType) {
	createTableQuery = R"(
	CREATE TABLE IF NOT EXISTS Students (
	id INTEGER PRIMARY KEY,
	name VARCHAR(255) NOT NULL,
	description VARCHAR(255) NOT NULL,
	avatar BLOB
	)
	)";
	} else { // For other database types like MySQL
	createTableQuery = R"(
	CREATE TABLE IF NOT EXISTS Students (
	id INT AUTO_INCREMENT PRIMARY KEY,
	name VARCHAR(255) NOT NULL,
	description VARCHAR(255) NOT NULL,
	avatar LONGBLOB DEFAULT NULL
	)
	)";
	}
	if (!query.exec(createTableQuery)) {
	qDebug() << "Error: Failed to create table" << query.lastError().text();
	}
	}
	void StudentDBHandler::addStudent(const std::string_view &name,
	const std::string_view &description,
	const std::string_view &imagePath)
	{
	QSqlDatabase db = getDatabaseConnection();
	if (!db.isOpen()) {
	qDebug() << "Error: Failed to connect to database";
	return;
	}
	createTableIfNotExists(db);
	QSqlQuery query(db);
	query.prepare("INSERT INTO Students (name, description, avatar) VALUES (:name, :description, :avatar)");
	query.bindValue(":name", name.data());
	query.bindValue(":description", description.data());
	if (!imagePath.empty()) {
	QFile file(imagePath.data());
	if (!file.open(QIODevice::ReadOnly)) {
	qDebug() << "Error: Failed to open image file" << imagePath;
	return;
	}
	QByteArray imageData = file.readAll();
	query.bindValue(":avatar", imageData);
	} else {
	query.bindValue(":avatar", QVariant(QVariant::ByteArray));
	}
	if (!query.exec()) {
	qDebug() << "Error: Failed to add student" << query.lastError().text();
	} else {
	qDebug() << "Student added successfully";
	}
	db.close();
	}
	void StudentDBHandler::listStudents()
	{
	auto students = getStudents();
	for (const auto student : students) {
	qDebug() << student.studentId_ << "Name:" << student.name_
	<< "Description:" << student.description_;
	}
	}
	std::vector<Student> StudentDBHandler::getStudents()
	{
	QSqlDatabase db = getDatabaseConnection();
	if (!db.isOpen()) {
	throw std::runtime_error("Error: Failed to connect to database");
	}
	QSqlQuery query(db);
	if (!query.exec("SELECT * FROM Students")) {
	throw std::runtime_error("Error: Failed to retrieve students"
	+ query.lastError().text().toStdString());
	}
	QSqlRecord record = query.record();
	const auto idIndex = record.indexOf("id");
	const auto nameIndex = record.indexOf("name");
	const auto descriptionIndex = record.indexOf("description");
	const auto avatarIndex = record.indexOf("avatar");
	std::vector<Student> students;
	while (query.next()) {
	Student student;
	student.studentId_ = query.value(idIndex).toInt();
	student.name_ = query.value(nameIndex).toString().toStdString();
	student.description_ = query.value(descriptionIndex).toString().toStdString();
	QPixmap pixmap;
	pixmap.loadFromData(query.value(avatarIndex).toByteArray());
	student.avatar_ = std::move(pixmap);
	students.emplace_back(std::move(student));
	}
	db.close();
	return students;
	}
	QSqlDatabase StudentDBHandler::getDatabaseConnection()
	{
	static int nextDbConnectionNumber{}; /// to disable DB warning: https://stackoverflow.com/questions/55199965/qsqldatabase-how-to-avoid-qt-sql-default-connection-still-in-use-duplicate
	QSqlDatabase db = QSqlDatabase::addDatabase(m_dbType.c_str(),
	"connection_" + QString::number(nextDbConnectionNumber++));
	db.setDatabaseName(m_dbName.c_str());
	if (m_dbType == "QMYSQL") {
	db.setHostName(m_dbHost.c_str());
	db.setUserName(m_dbUser.c_str());
	db.setPassword(m_dbPassword.c_str());
	}
	if (!db.open()) {
	qDebug() << "Error: Failed to connect to database";
	}
	return db;
	}

view raw studentdbhandler.cpp hosted with ❤ by GitHub

	#ifndef STUDENTDBHANDLER_H
	#define STUDENTDBHANDLER_H
	#include <string>
	#include <string_view>
	#include <vector>
	#include <optional>
	class QSqlDatabase;
	class QPixmap;
	struct Student {
	int studentId_;
	std::string name_, description_;
	std::optional<QPixmap> avatar_;
	};
	class StudentDBHandler {
	public:
	StudentDBHandler(const std::string& dbType, const std::string& dbName, const std::string& dbHost = "",
	const std::string& dbUser = "", const std::string& dbPassword = "")
	: m_dbType(dbType), m_dbName(dbName), m_dbHost(dbHost), m_dbUser(dbUser), m_dbPassword(dbPassword) {}
	void addStudent(const std::string_view& name, const std::string_view& description, const std::string_view& imagePath = "");
	std::vector<Student> getStudents();
	void listStudents();
	private:
	void createTableIfNotExists(QSqlDatabase& db);
	QSqlDatabase getDatabaseConnection();
	std::string m_dbType;
	std::string m_dbName;
	std::string m_dbHost;
	std::string m_dbUser;
	std::string m_dbPassword;
	};
	#endif // STUDENTDBHANDLER_H

view raw studentdbhandler.h hosted with ❤ by GitHub

1. Wygodnym programem do przeglądania bazy danych jest: Dbeaver
2. Polecam sobie aktywować bazę danych MySQL (dostępna przez https://panel.agh.edu.pl/)
   • Aby się połączyć z bazą danych potrzebny VPN AGH.
   • Alternatywnie można skorzystać z bazy danych SQLite, która działa lokalnie.
3. Samo dodanie plików do projektu może spowodować błędy kompilacji! Dlatego trzeba jeszcze w pliku CMakeLists.txt dodać komponenty QT korzystające z bazy danych. Czyli człon Sql:
   find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Widgets Sql)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets Sql)
find_package(Qt6 REQUIRED COMPONENTS Sql)
   Oraz też kod przy linkowaniu:
   target_link_libraries(AplikacjaNaWarsztatyPrototyp PRIVATE Qt${QT_VERSION_MAJOR}::Widgets Qt${QT_VERSION_MAJOR}::Sql)