I have an app which allows me to find files containing a certain phrase.
When i click on the submit Button the content of the QTableView should disappear and i fill the Table in a function.

Code: gui.cpp

GUI::GUI(QWidget* parent) : QWidget(parent),
    path(new QLabel("nnPath to directory", this)),
    welcome(new QLabel("Application is finding log files with a given phrase.", this)),
    text(new QLabel("nHello World", this)),
    searchword(new QLabel("nSearch phrase", this)),
    path_edit(new QLineEdit(this)),
    searchword_edit(new QLineEdit(this)),
    output_view(new QTableView(this)),
    output_model(new QStandardItemModel(0, 3, this)),
    submitButton(new QPushButton("Click/press Enter to get files")),
    browseButton(new QPushButton("Browse....")),
    reset_Dir(new QPushButton("Reset Directory"))
{
    setWindowTitle("Log File Search Application");
    setBaseSize(2000, 1100);

    QVBoxLayout* mainLayout = new QVBoxLayout(this);
    QString default_path ="a path";
    
    //QLabel
    welcome->setStyleSheet("color: black; font: bold 55px;");
    text->setStyleSheet("color: black; font: 35px;");
    path->setStyleSheet("font: 25px;");
    searchword->setStyleSheet("font:25px;");
    //QLineEdit
    path_edit->setStyleSheet("font:25px; height: 50px;");
    path_edit->setText(default_path);
    searchword_edit->setStyleSheet("font:25px; height: 50px;");
    //QPushButton
    submitButton->setStyleSheet("background: darkgrey; height: 70px; width: 250px; font: 20px;");
    browseButton->setStyleSheet("background: darkgrey; height: 40px; font: 20px;");
    reset_Dir->setStyleSheet("background: darkgrey; height: 40px; font: 20px;");

    //Output
    output_model->setHorizontalHeaderLabels(QStringList() << "Date" << "Time" << "Filepath");

    output_view->setModel(output_model);
    output_view->setStyleSheet("background-color: white; font: 16px; color: black;");
    output_view->setColumnWidth(0, width() / 3);
    output_view->setColumnWidth(1, width() / 3);
    output_view->horizontalHeader()->setSectionResizeMode(2, QHeaderView::Stretch);     //column stretches when window is resized
    output_view->setSortingEnabled(true);                                               //sorting table columns
    output_view->setFocusPolicy(Qt::NoFocus);                                           //TabFocus is never set at QTableView

    //QHBoxLayout: /questions/42100394/how-to-align-children-in-a-qhboxlayout-left-center-and-right
    QHBoxLayout* path_layout = new QHBoxLayout();
    path_layout->addWidget(path_edit, 3);
    path_layout->addWidget(browseButton, 0.1);
    path_layout->addWidget(reset_Dir, 0.1);

    QHBoxLayout* searchBtn_layout = new QHBoxLayout();
    searchBtn_layout->addWidget(submitButton);
    searchBtn_layout->addStretch();

    //to 'click' with Keyboard
    submitButton->setAutoDefault(true);
    browseButton->setAutoDefault(true);
    reset_Dir->setAutoDefault(true);

    //connections
    connect(browseButton, &QPushButton::clicked, this, &GUI::getDir);
    connect(submitButton, &QPushButton::clicked, this, &GUI::checkInput);
    connect(searchword_edit, &QLineEdit::returnPressed, this, &GUI::checkInput);
    connect(path_edit, &QLineEdit::returnPressed, this, &GUI::checkInput);
    connect(reset_Dir, &QPushButton::clicked, this, &GUI::resetDir);

    //add to VBox
    mainLayout->addWidget(welcome);
    mainLayout->addWidget(text);
    mainLayout->addWidget(path);
    mainLayout->addLayout(path_layout);
    mainLayout->addWidget(searchword);
    mainLayout->addWidget(searchword_edit);
    mainLayout->addLayout(searchBtn_layout);
    mainLayout->addWidget(output_view);

    setTabOrder(path_edit, browseButton);
    setTabOrder(browseButton, reset_Dir);
    
    setLayout(mainLayout);
}

void GUI::checkInput() {

    QMessageBox msg;
    if (path_edit->text().isEmpty() && searchword_edit->text().isEmpty()) {
        msg.setText("You need to fill out the form!");
        msg.exec();
    }
    else if (path_edit->text().isEmpty())
    {
        msg.setText("You need to give a path!");
        msg.exec();
    }
    else if (searchword_edit->text().isEmpty())
    {
        msg.setText("You need to give a phrase!");
        msg.exec();
    }
    else
    {
        validInput(path_edit, searchword_edit, output_model, output_view);
    }
}

void GUI::validInput(QLineEdit* path, QLineEdit* search, QStandardItemModel* model, QTableView* view) {

    QString qstr = path->text();
    std::string path_string = qstr.toStdString();

    QString qstr2 = search->text();
    std::string search_string = qstr2.toStdString();

    callDir(path_string, search_string, model, view);
}

void GUI::getDir() {
    QString default_path = "C:/Users/sehos/AppData/Local/CADstar/CS.Core/cache/logs";
    
    QString dirPath = QFileDialog::getExistingDirectory(nullptr, tr("Open Dir"), QDir::currentPath());
    
    if (!dirPath.isEmpty()) path_edit->setText(dirPath);
}

detection.cpp

namespace fs = std::filesystem;

bool checkForWord(std::string filename, std::string word, std::set<std::string>& files) {
    int offset;
    std::string line;
    std::ifstream file;

    file.open(filename);
    if (file.is_open()) {
        bool validWord = false;                                        
        while (getline(file, line)) {
            if ((offset = line.find(word, 0)) != std::string::npos) {
                files.insert("n" + filename);
                validWord = true;
            }
        }
        file.close();
        return validWord;
    }
    else QMessageBox::warning(nullptr, "File not found!", "File could not be opened!");
}

void printOutput(std::set<std::string> files, QStandardItemModel* model, QTableView* view)
{
    
    model->setRowCount(files.size());
    int row = 0;
    
    for (const auto& str : files)
    {
        //extracting filename from filepath
        size_t lastSlash = str.find_last_of("/\");
        if (lastSlash == std::string::npos) lastSlash = -1;
        std::string fName = str.substr(lastSlash +1);           //YYYY-MM-DD_hh-mm-ss.txt

        size_t timeUnderScore = fName.find("_");
        std::string time = fName.substr(timeUnderScore+1,8);
        std::replace(time.begin(), time.end(), '-', ':');       //hh-mm-ss -> hh:mm:ss
        
        size_t dateUnderScore = fName.find("_");
        std::string date = fName.substr(0,dateUnderScore);
        std::replace(date.begin(), date.end(), '-', '/');       //YYYY-MM-DD -> YYYY/MM/DD

        //creating QStandardItem to set in QTableView
        auto* displayDate = new QStandardItem(QString::fromStdString(date));
        auto* displayTime = new QStandardItem(QString::fromStdString(time));
        auto* fileItem = new QStandardItem(QString::fromStdString(str));

        //flags to set the Table read-only
        displayDate->setFlags(Qt::ItemIsEditable);
        displayTime->setFlags(Qt::ItemIsEditable);
        fileItem->setFlags(Qt::ItemIsEditable);

        
        model->setItem(row, 0, displayDate);
        model->setItem(row, 1, displayTime);
        model->setItem(row, 2, fileItem);

        //Output with QMessageBox 
        /*
            std::string combine;
            for (const auto& str : files) {
                combine += str + "n";
            }
            //The Filepaths are printed.
            QMessageBox msg;
            QString filestr = QString::fromStdString(combine);
            msg.setText(QString::fromStdString(combine));
            msg.exec();
        */
        row++;
    }
}

void callDir(std::string dir, std::string search, QStandardItemModel* model, QTableView* view) {         
    std::string folderPath = dir;
    std::set<std::string> txtFiles;                      
    std::set<std::string> files;
    bool validW = false;       
    view->clearMask();

    try {
        for (const auto& entry : fs::directory_iterator(folderPath)) {
            if (entry.path().extension() == ".txt") txtFiles.insert(entry.path().string());      
        }
    }
    catch (const std::exception& e)
    {
        QMessageBox::critical(nullptr, "Invalid Path", "Path is invalid!!");
    }

    for (const std::string& file : txtFiles) {
        if (checkForWord(file, search, files)) validW = true;
    }

    if (!validW) QMessageBox::critical(nullptr, "Word not found", QString("The word '%1' given could not be found in any files.").arg(QString::fromStdString(search)));
    else if (!files.empty()) printOutput(files, model, view); 
}

I already tried using

`model->clear();
model->removeRows(0, output_model->rowCount());`

Maybe I placed it in the wrong place when it should work but it did not work for me.