qt-signal-problem expression cannot be used as a function

#ifndef SETTINGWIDGET_H
#define SETTINGWIDGET_H

#include <QWidget>
#include <QLabel>
#include <QCheckBox>
#include <QSpinBox>
#include <QScrollArea>
#include <QStringList>
#include <QLineEdit>
#include <QPlainTextEdit>
#include <QSettings>
#include <QGridLayout>
#include <qdebug.h>
#include <QComboBox>
#include <QPushButton>

class ledSetting : public QWidget{
    Q_OBJECT
public:
    int id;
    QCheckBox *dimable;
    QLineEdit *name;
    explicit ledSetting(int id,QWidget *parent=0):QWidget(parent){
        QSettings settings("energiewandler", "settingwidget");
        dimable = new QCheckBox("Dim");
        dimable->setChecked(settings.value("settingsLed"+QString::number(id)+"Dimmable",QVariant(true)).toBool());
        name=new QLineEdit();
        name->setText(settings.value("LED"+QString::number(id)+"Label",QVariant("LED"+QString::number(id))).toString());
        name->setPlaceholderText("Put a name for your led inside...");
        QGridLayout *innerLayout = new QGridLayout();
        innerLayout->addWidget(name,0,0);
        innerLayout->addWidget(dimable,0,1);
        this->setLayout(innerLayout);
        //appSettings.setValue("settingsLed2Dimmable",ui->settingsDimmableLED2->isChecked());
        //onSettingsLedDim(appSettings.value("dimmableLedCount",2).toInt());
        connect(dimable,SIGNAL(clicked(bool)),this,SLOT(onDim()));
        connect(name,SIGNAL(textChanged(QString)),this,SLOT(onName()));
    }

public slots:
    void onDim(){
        QSettings settings("energiewandler", "settingwidget");
        settings.setValue("settingsLed"+QString::number(id)+"Dimmable",dimable->isChecked());
    }

    void onName(){
        QSettings settings("energiewandler", "settingwidget");
        settings.setValue("LED"+QString::number(id)+"Label",name->text());
    }
};

class settingWidget : public QWidget
{
    Q_OBJECT
private slots:
    void onTerminalCompleter();
   void onNrOfLeds22();

public:
    explicit settingWidget(QWidget *parent = 0);
    QSpinBox *nrOfLeds;
    ledSetting *led1;
    ledSetting *led2;
    ledSetting *led3;
    QPlainTextEdit *terminalCompleter;
    QComboBox *interfaces,*devices;
    QPushButton *refresh,*connect;


};

#endif // SETTINGWIDGET_H


/*
******************************************
settingwidget.cpp
******************************************
*/

#include "settingwidget.h"

settingWidget::settingWidget(QWidget *parent) : QWidget(parent) {
  QSettings settings("energiewandler", "settingwidget");
  nrOfLeds = new QSpinBox();
  nrOfLeds->setValue(settings.value("dimmableLedCount", QVariant(2)).toInt());
  QGridLayout *innerLayout = new QGridLayout();
  innerLayout->addWidget(new QLabel("Nr of leds: "), 0, 0);
  innerLayout->addWidget(nrOfLeds, 0, 1);
  int nextNr = 1;
  if (nrOfLeds->value() > 0) {
    led1 = new ledSetting(1);
    innerLayout->addWidget(led1, 1, 0);
    nextNr++;
  }
  if (nrOfLeds->value() > 1) {
    led2 = new ledSetting(2);
    innerLayout->addWidget(led2, 2, 0);
    nextNr++;
  }
  if (nrOfLeds->value() > 2) {
    led3 = new ledSetting(3);
    innerLayout->addWidget(led3, 3, 0);
    nextNr++;
  }
  terminalCompleter = new QPlainTextEdit(parent);

  terminalCompleter->setPlaceholderText("Place your completments for the "
                                        "terminal in a list here. Every line "
                                        "is a completment.");
  QString line;
  QSettings tSettings("energiewandler", "terminalwidget");
  foreach (line, tSettings.value("terminalCompleter").toStringList()) {
    terminalCompleter->appendPlainText(line);
  }
  innerLayout->addWidget(new QLabel("Terminal-Completer"), nextNr, 0);
  innerLayout->addWidget(terminalCompleter, nextNr + 1, 0);

  // connect(terminalCompleter,SIGNAL(textChanged()),this,SLOT(onTerminalCompleter()));
  QScrollArea *scroll = new QScrollArea();
  scroll->setLayout(innerLayout);
  connect(terminalCompleter, SIGNAL(textChanged()), this, SLOT(onNrOfLeds22()));
  connect(this->nrOfLeds, SIGNAL(valueChanged(int)), this,
          SLOT(onNrOfLeds22()));
  QGridLayout *outerLayout = new QGridLayout();
  outerLayout->addWidget(scroll, 0, 0);

  this->setLayout(outerLayout);
}

void settingWidget::onNrOfLeds22() {
  QSettings settings("energiewandler", "settingwidget");
  settings.setValue("dimmableLedCount", nrOfLeds->value());
}

void settingWidget::onTerminalCompleter() {
  QSettings settings("energiewandler", "terminalwidget");
  settings.setValue("terminalCompleter",
                    terminalCompleter->toPlainText().split("\n"));
}