My first own Qt app

tomy

Hi all,

Please look at these files. These are the files of an app that I want to develop and extent it gradually. Now is the first steps.

This is employee.h:

#ifndef EMPLOYEE_H
#define EMPLOYEE_H

#include <QDialog>

class QLabel;
class QPushButton;
class QLineEdit;

class Employee : public QDialog
{
    Q_OBJECT
public:
    Employee(QWidget* parent = 0);
private:
    int mySalary;
    QLabel* label;
    QLineEdit* lineEdit;
    QPushButton* show_sl;
    QPushButton* quit;
};

#endif // EMPLOYEE_H

And this is employee.cpp:

#include <QtWidgets>
#include "employee.h"

Employee::Employee(QWidget* parent)
         :QDialog(parent)
{
     mySalary = 15;
     
     label = new QLabel(tr("mySalary"));
     lineEdit = new QLineEdit;
     show_sl = new QPushButton(tr("Show"));
     quit = new QPushButton(tr("Close"));


     QHBoxLayout* layout1 =new QHBoxLayout;
     layout1 -> addWidget(label);
     layout1 -> addWidget(lineEdit);

     QHBoxLayout* layout2 =new QHBoxLayout;
     layout2 -> addWidget(show_sl);
     layout2 -> addWidget(quit);

     QVBoxLayout* vlayout = new QVBoxLayout;
     vlayout -> addLayout(layout1);
     vlayout -> addLayout(layout2);

     setLayout(vlayout);
}

And this is main.cpp:

#include <QApplication>
#include "employee.h"

int main(int argc , char* argv[])
{
    QApplication app(argc, argv);
    Employee* employee = new Employee;
    employee -> show();
    return app.exec();
}

It runs successfully. Now my question is that, what widgets/functions/slots/signal do I need to add to the code so that when I click the Show button, it shows the value of my_Salary which is 15 in the lineEdit please?
As I said, I'm going to make the app bigger step-by-step.

raven-worx

@tomy
you could add a method to set your values before you call show()

Very basic example:

class Employee : public QDialog
{
    Q_OBJECT
public:
    Employee(QWidget* parent = 0);

    void setSalary(int value) {
            mySalary = value;
            lineEdit->setText( QString::number(value) );
    }
    ...
};

employee = new Employee;
employee->setSalary(15);

tomy

@raven-worx
Thank you for your reply but I want to use the widgets in my code, and as I said, by clicking the button named Show , its value to be shown in lineEdit .
Show is in line show_sl = new QPushButton(tr("Show")); in employee.cpp .

I later develop the code and add some function to be able to set the salary.

VRonin

at the bottom of the constructor add
connect(show_sl,&QPushButton::clicked,[this]()->void{my_Salary->setText( QString::number(mySalary ));});

tomy

What are these??!!
I'm new in Qt and you write things like &QPushButton::clicked,[this]()->void .... I don't understand these, sorry.

I think I need a signal and a slot like this:
I added these to the employee.h

signals:
    void show_salary();
private slots:
    void show_salary_in_lineEdit();

And a connect and the definition of show_salary_in_lineEdit() to the employee.cpp this way

connect(show_sl, SIGNAL(show_salary()), lineEdit,
            SLOT(show_salary_in_lineEdit()));
.
.
.

void Employee::show_salary_in_lineEdit()
{
   lineEdit -> setText(QString::number(mySalary));
}

Now the code runs but clicking the Show button doesn't do anything!

mrjj

Hi
When you use SIGNAL and SLOT macros, you can check if connect works with
qDebug() << "conn:" << connect ( xxx );
should return true;

VRonin

@tomy said in My first own Qt app:

What are these??!!

That's the Qt5 connection syntax with a lambda

I think I need a signal and a slot

You just need a slot

connect(show_sl, SIGNAL(show_salary())

show_sl has no signal show_salary hence @mrjj remark warning you that the connect won't work

this is correct

void Employee::show_salary_in_lineEdit()
{
   lineEdit -> setText(QString::number(mySalary));
}

now the connect:

connect(
show_sl //who sends the signal
, &QPushButton::clicked // what signal do you want to react to (in this case when the button is clicked)
,this // who should catch the signal
,&Employee::show_salary_in_lineEdit //what slot should be called
);

mlago

Hi,
Your connect code not is correc, what you need is connect de Button signal clicked with your Show function,Something like that:

 connect(show_sl, SIGNAL(clicked(bool)), this, SLOT(show_salary_in_lineEdit()));

How to Use QPushButton

If you allow me a question, would not it be easier for you to use the graphic editor instead of creating the graphic objects by code?

EDIT: I am sorry, I was responding when the @VRonin had already done so.

calebhalvy

@mlago,
@VRonin is using the new Qt5 Signal/Slot connection syntax, as he linked to here.

tomy

@mlago said in My first own Qt app:

Hi,
Your connect code not is correc, what you need is connect de Button signal clicked with your Show function,Something like that:
 connect(show_sl, SIGNAL(clicked(bool)), this, SLOT(show_salary_in_lineEdit()));
How to Use QPushButton

Thank you. I changed the connect the way you showed and the code ran as expected. Thanks again.

If you allow me a question, would not it be easier for you to use the graphic editor instead of creating the graphic objects by code?

I'm learning Qt using a book and it walks me this way. I will be taught the Designer mode shortly. :)

EDIT: I am sorry, I was responding when the @VRonin had already done so.

tomy

@mrjj said in My first own Qt app:

Hi
When you use SIGNAL and SLOT macros, you can check if connect works with
qDebug() << "conn:" << connect ( xxx );
should return true;

Thanks. Although the code runs fine now, let me ask how to use that code for example in my code? (instructions)

mrjj

@tomy
Hi
You can use qDebug() for many nice things :)

1: #include <QDebug>

2: use it

qDebug() << "text" << variable << "more text" << some_other_variable ;

tomy

Thank you.