horizontalScrollBar() Error

[IknowQT]

QTScrollArea::QTScrollArea(QWidget *parent)
{
	ui.setupUi(this);

	//m_pTimer = new QTimer(this);
	//connect(m_pTimer, SIGNAL(timeout()), this, SLOT(UpdateTick()));
	//m_pTimer->start(500);
	
	// 사이즈 (400, 250)
	this->ui.scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
	this->ui.scrollArea->grabGesture(Qt::TapGesture);

	m_pWidget = new QWidget(this->ui.scrollArea);
	this->ui.scrollArea->setWidget(m_pWidget);

	QHBoxLayout* layout = new QHBoxLayout();
	m_pWidget->setLayout(layout);
	layout->setContentsMargins(QMargins(0, 0, 0, 0));
	layout->setSpacing(0);

	for (int i = 0; i < 30; i++)
	{
		QPushButton* pbtn = new QPushButton(QString("%1").arg(i));
		pbtn->setFixedSize(400 / 6, 200);

		layout->addWidget(pbtn);
	}

	this->connect(this->ui.pushButton, &QPushButton::clicked, this, &QTScrollArea::BtnPrev);
	this->connect(this->ui.pushButton_2, &QPushButton::clicked, this, &QTScrollArea::BtnNext);

	this->ui.scrollArea->horizontalScrollBar()->setValue(1);   // C2027 Error
}

An error has occurred.
Isn't horizontalScrollBar also created when creating scrollArea objects? Why does it say that you used an undefined format?

[eyllanesc]

@IknowQT add #include <QScrollBar>