[QT]example4-Widget-database(SQLite)

👉 아래는 위젯 방식의 경우 입니다.
Below is the widget method.

1.UI디자인 / UI Desing

2.mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

// 코드 추가 / Add code to here
#include <QStringListModel>


QT_BEGIN_NAMESPACE
namespace Ui {
class MainWindow;
}
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;

    // --> 코드 추가 / Add cod to here

    void loadData(); // 데이터로딩 / data loding
    void deleteSelectedRecord(); // db레코드 삭제 / delete db record
    void deleteAllRecord(); // 모든 데이터 삭제 / Delete all data
    QStringListModel *model; // 멤버로 객체로 선언 / Declare as an object with a member

    //<-- 여기까지 / up to here

};
#endif // MAINWINDOW_H

3.main.cpp

#include "mainwindow.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

4.mainwindow.cpp

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

// 코드추가 / Add code
#include <QSqlDatabase>
#include <QSqlQuery>
#include <QStringListModel>
#include<QMessageBox>
#include <QSqlError>


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

    //-- 여기서부터 코드 추가 / Add code from here

    // DB 연결 / DB Connection
    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
    db.setDatabaseName("localdata.db");
    db.open();

    // 테이블 생성 / Create Table
    QSqlQuery query;
    query.exec("CREATE TABLE IF NOT EXISTS records (id INTEGER PRIMARY KEY, text1 TEXT, text2 TEXT)");

    // 버튼 클릭 시 저장(시그널 슬롯)
    // Save data on button click (signal slot).
    connect(ui->pushButton, &QPushButton::clicked, this, [=]() {
        QString t1 = ui->textEdit->toPlainText();
        QString t2 = ui->plainTextEdit->toPlainText();

        QSqlQuery q;
        q.prepare("INSERT INTO records (text1, text2) VALUES (?, ?)");
        q.addBindValue(t1);
        q.addBindValue(t2);
        q.exec();

        // QTextEdit을 비웁니다.
        ui->textEdit->clear();
        ui->plainTextEdit->clear();

        loadData(); // 리스트 갱신
    });

    // 데이터 삭제 버튼 / Delete data button
    connect(ui->pushButton_2, &QPushButton::clicked, this, [=]() {
        deleteSelectedRecord();
    });

    // 모든 데이터 삭제 버튼 / Delete all data button
    connect(ui->pushButton_3, &QPushButton::clicked, this, [=]() {
        deleteAllRecord();
    });

    //connect(ui->pushButton_2, &QPushButton::clicked, this, &MainWindow::deleteSelectedRecord);

    loadData(); // 초기 로딩 / data loading

    //-- 여기까지 / Up to here...

}


//--> 코드 추가 / 여기서부터 코드 추가 / Add code from here

// 데이터로드 / data loading
void MainWindow::loadData() {

    QStringList items;
    QSqlQuery query("SELECT text1, text2 FROM records");
    while (query.next()) {
        items << query.value(0).toString() + " | " + query.value(1).toString();
    }

    // 멤버변수로 사용 / Used as a member variable
    // 멤버 변수 초기화 / Initialize member variables
    model = new QStringListModel(items,this);

    // 리스트뷰에 연결 / Connect to list view
    ui->listView->setModel(model);

   // 지역변수사용
   // QStringListModel *model = new QStringListModel(items, this);
   // ui->listView->setModel(model);
}

// 레코드 삭제 / delete record
void MainWindow::deleteSelectedRecord() {
    QModelIndex index = ui->listView->currentIndex();
    if (!index.isValid()) {
        QMessageBox::warning(this, "삭제 오류/Delete error", "삭제할 항목을 선택하세요/Select the items you want to delete.");
        return;
    }

    QString selectedText = model->data(index, Qt::DisplayRole).toString();

    QStringList parts = selectedText.split(" | ");
    if (parts.size() != 2) {
        QMessageBox::warning(this, "삭제 오류/Delete error", "항목 형식이 올바르지 않습니다./The item format is incorrect.");
        return;
    }

    QString text1 = parts[0].trimmed();
    QString text2 = parts[1].trimmed();

    // deburging
    //QMessageBox::warning(this, text1, text2);

    QSqlQuery query;

    // :text1,:text2는 바인딩 변수
    // :text1,:text2 are binding variables
    query.prepare("DELETE FROM records WHERE text1 = :text1 AND text2 = :text2");
    query.bindValue(":text1", text1);
    query.bindValue(":text2", text2);

    if (!query.exec()) {
        QMessageBox::critical(this, "DB 오류/DB error", query.lastError().text());
        return;
    }

    // 삭제 후 리스트 갱신
    // Update list after deletion
    loadData();

}

// 모든 데이터 삭제
// Delete all data
void MainWindow::deleteAllRecord() {
    QSqlQuery query;
    query.prepare("DELETE FROM records");

    if (!query.exec()) {
        QMessageBox::critical(this, "DB 오류/DB error", query.lastError().text());
        return;
    }

    // 삭제 후 리스트 갱신
    // Update list after deletion
    loadData();

}

//<-- 여기까지 / Up to here

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

CMakeLists.txt

cmake_minimum_required(VERSION 3.16)

project(example4 VERSION 0.1 LANGUAGES CXX)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Widgets)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets)

#-- sqlite 모듈 추가 /  Add sqlite module
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Core Widgets Sql)


set(PROJECT_SOURCES
        main.cpp
        mainwindow.cpp
        mainwindow.h
        mainwindow.ui
)

if(${QT_VERSION_MAJOR} GREATER_EQUAL 6)
    qt_add_executable(example4
        MANUAL_FINALIZATION
        ${PROJECT_SOURCES}
    )
# Define target properties for Android with Qt 6 as:
#    set_property(TARGET example4 APPEND PROPERTY QT_ANDROID_PACKAGE_SOURCE_DIR
#                 ${CMAKE_CURRENT_SOURCE_DIR}/android)
# For more information, see https://doc.qt.io/qt-6/qt-add-executable.html#target-creation
else()
    if(ANDROID)
        add_library(example4 SHARED
            ${PROJECT_SOURCES}
        )
# Define properties for Android with Qt 5 after find_package() calls as:
#    set(ANDROID_PACKAGE_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/android")
    else()
        add_executable(example4
            ${PROJECT_SOURCES}
        )
    endif()
endif()

# -- sqlite 링크 / sqlite linke
target_link_libraries(example4 PRIVATE
    Qt${QT_VERSION_MAJOR}::Core
    Qt${QT_VERSION_MAJOR}::Widgets
    Qt${QT_VERSION_MAJOR}::Sql
)


target_link_libraries(example4 PRIVATE Qt${QT_VERSION_MAJOR}::Widgets)

# Qt for iOS sets MACOSX_BUNDLE_GUI_IDENTIFIER automatically since Qt 6.1.
# If you are developing for iOS or macOS you should consider setting an
# explicit, fixed bundle identifier manually though.
if(${QT_VERSION} VERSION_LESS 6.1.0)
  set(BUNDLE_ID_OPTION MACOSX_BUNDLE_GUI_IDENTIFIER com.example.example4)
endif()
set_target_properties(example4 PROPERTIES
    ${BUNDLE_ID_OPTION}
    MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
    MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
    MACOSX_BUNDLE TRUE
    WIN32_EXECUTABLE TRUE
)

include(GNUInstallDirs)
install(TARGETS example4
    BUNDLE DESTINATION .
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)

if(QT_VERSION_MAJOR EQUAL 6)
    qt_finalize_executable(example4)
endif()

5.실행 / run