SIGNAL fail when debug started - c++

Question

I have an issue using the connection stuff of Qt5.
I posted here some code to give a quick view:
void MainWindow::onMessage(const Message* message) {
try {
const TextMessage* textMessage = dynamic_cast<const TextMessage*> (message);
std::string text = "";
if (textMessage != NULL) {
text = textMessage->getText();
} else {
text = "NOT A TEXTMESSAGE!";
}
int fieldIndex=message->getIntProperty("field");
QString qstr = QString::fromStdString(text);
switch(fieldIndex)
{
case 0:ui->lineEdit->setText(qstr);break;
case 1:ui->lineEdit_2->setText(qstr);break;
case 2:ui->lineEdit_3->setText(qstr);break;
case 3:ui->lineEdit_4->setText(qstr);break;
case 4:ui->lineEdit_5->setText(qstr);break;
case 5:ui->lineEdit_6->setText(qstr);break;
case 6:ui->lineEdit_7->setText(qstr);break;
case 7:ui->lineEdit_8->setText(qstr);break;
case 8:ui->lineEdit_9->setText(qstr);break;
}
connect(ui->lineEdit_4,SIGNAL(textChanged(qstr)),ui->widget_diagram2,SLOT(upDateDatas(qstr)));
}catch (CMSException& e) {
e.printStackTrace();
}
}
As you can see I'm trying to connect the signal textChanged generated by the lineEdit_4 with the ui object widget_diagram2 and execute the slot upDateDatas(qstr). But something bad happens, because I received this message:
QObject::connect: No such signal QLineEdit::textChanged(qstr) in mainwindow.cpp:97
QObject::connect: (sender name: 'lineEdit_4')
QObject::connect: (receiver name: 'widget_diagram2')
personally I don't know why....where is the error?
void MainWindow::upDateDatas(QString qstr){
bool ok;
double value0=qstr.toDouble(&ok);
double key = QDateTime::currentDateTime().toMSecsSinceEpoch()/1000.0;
static double lastPointKey = 0;
if (key-lastPointKey > 0.01) // at most add point every 10 ms
{
ui->widget_diagram2->graph(0)->addData(key, value0);
ui->widget_diagram2->graph(0)->removeDataBefore(key-8);
ui->widget_diagram2->graph(0)->rescaleValueAxis();
lastPointKey = key;
}
ui->widget_diagram2->xAxis->setRange(key+0.25, 8, Qt::AlignRight);
//ui->widget_diagram2->replot();
}
and this is the error:
QObject::connect: No such slot QCustomPlot::upDateDatas(QString) in mainwindow.cpp:97
QObject::connect: (sender name: 'lineEdit_4')
QObject::connect: (receiver name: 'widget_diagram2')
.h file:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QTimer>
#include <activemq/library/ActiveMQCPP.h>
#include <decaf/lang/Thread.h>
#include <decaf/lang/Runnable.h>
#include <decaf/util/concurrent/CountDownLatch.h>
#include <decaf/lang/Integer.h>
#include <decaf/lang/Long.h>
#include <decaf/lang/System.h>
#include <activemq/core/ActiveMQConnectionFactory.h>
#include <activemq/util/Config.h>
#include <cms/Connection.h>
#include <cms/Session.h>
#include <cms/TextMessage.h>
#include <cms/BytesMessage.h>
#include <cms/MapMessage.h>
#include <cms/ExceptionListener.h>
#include <cms/MessageListener.h>
#include "qcustomplot.h"
#include "IfacomAmqReceiver.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow, public MessageListener
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
void connectionReceiver();
void onMessage(const Message*);
void setupDiagram();
IfacomAmqReceiver* m_IfacomAmqListener;
private:
Ui::MainWindow *ui;
private slots:
void upDateDatas(QString);
};
#endif // MAINWINDOW_H

Answer 1

You call to connect() is wrong. It should be:
connect(ui->lineEdit_4, SIGNAL(textChanged(QString)),
ui->widget_diagram2, SLOT(upDateDatas(QString)));
Pay attention that inside connect you should pass types rather then variables names. Constant references const type & are OK, but ideally should be elided to yield type - it saves on typing, and is what connect internally does anyway.