Qt C ++中的组合框选择插槽和信号

Question

Trying to connect the new selection change in a QComboBox to use the string of that selection in a slot.

Basically, after the currentIndexChanged signal, the displayData mapp will already hold all data populated from another part of the program (eg a parser) and then, using the current selection of the combo box in comboBoxChange , a key will be given to the displayData map in order to get the desired values in the form of the tset struct.

Below is all my code setup and attempts slot and connect signals. Please help understand how to do it.

mainwindow.h

struct tset {

  // struct declaration //

QString name;
double height;
}

class MainWindow : public QMainWindow {

private slots:

void comboBoxChange(QMap<QPair<QString, QString>, tset>&  displayData,  QString selection);
}

mainwindow.cpp

#include "mainwindow.h"

//connect(ui->comboBox, &QComboBox::currentIndexChanged(const QString&), this,&MainWindow:: comboBoxChange(QMap<QPair<QString, QString>, tset>, QString selection));

connect(ui-> comboBox, &QComboBox::currentIndexChanged, this, &MainWindow::on_ comboBoxChange(QMap<QPair<QString, QString>, tset>, QString));


void MainWindow:: comboBoxChange (QMap<QPair<QString, QString>, tset> &displayData, QString s) {
// use the selection string to decide which data to get from the QMap
// from s derive blah and blah2
tset test= = displayData.value(qMakePair(QString{"blah"}, QString{"blah2"}));

qDebug() << test.name << test.height;
}

Answer 1

In the cpp, you have to use the connection function that is inherited from the QObject base class.

connect(const QObject * sender, const char * signal, const QObject * receiver, const char * method):

1. sender: Pointer to the sender
2. signal: Definition of the signal. SIGNAL() macro with the name of the signal and the parameter
3. receiver: Pointer to the receiver
4. method: Definition of the receiver method. SIGNAL() or SLOT macro with the name of the receiver signal or function and the parameter of it.

Hint: The connection is set at runtime. There is no compiler error if the connection is not correct(Only a QDebug message)

connect(ui->comboBox, SIGNAL(currentIndexChanged(const QString&)), this, SLOT(comboBoxChange(const QString&)));

Here are the declaration in the header. You have forgot to mention Q_OBJECT at the top of the declaration. You need it for all classes that contain signals or slots.

class MainWindow : public QMainWindow
{
  Q_OBJECT

  private slots:
    void comboBoxChange(const QString& selection_text);
}