How can I solve this?

I have a GUI application which has a push button and text area.

what i want the app to do is, when i press a push button, it should call a function that i have written and display its return value in the text area.

this is the function

Code:

---

using namespace std;
 
char DLLfunction (){
         QLibrary myLib("dllprog");
         typedef char* (*MyPrototype)();
         MyPrototype myFunction =
         (MyPrototype) QLibrary::resolve("dllprog", "TestDll");
 
         char *b = myFunction();
         return b;
}

---

how can get the return value in the GUI and in the text area.

I am using QtCreator.

Hi,

Just get the return value into a QString and show it into the widget(QLineEdit, QTextEdit,...).

can you explain it a bit further??

I have developed a console application but I am new to GUI and I have no idea how to add the signals and slots.

thanks for replying

Hi,

You have a function called DLLfunction that returns a "char*", so:

Code:

---

QString qString(DLLfunction());

---

DLLfunction retunrs a "char*" and QString uses it to create the QString.

Then, you have the main window where you execute your code:

Code:

---

myMainWindow::someMethod()
{
  //Here you call your DLLfunction and show it to the QLineEdit
  QString qString(DLLfunction());
  ui.LineEdit->setText(qString);
}

---

Take a look at "lineedit" examples on Qt dir.

Code:

---

#include <QtGui/QApplication>
#include <QString>
#include <QLineEdit>
#include "dialog.h"
#include <QLibrary>
#include <iostream>
#include <windows.h>
 
using namespace std;
 
char DLLfunction()
{
    QLibrary myLib("dllprog");
    typedef char* (*MyPrototype)();
    MyPrototype myFunction =
    (MyPrototype) QLibrary::resolve("dllprog", "TestDll");
    char b = myFunction();
    return b;
}
 
QString qString(DLLfunction());
 
int main(int argc, char *argv[])
{
 
    QString qString(DLLfunction());
    ui.LineEdit->setText(qString);
 
    QApplication a(argc, argv);
    Dialog w;
    w.show();
    return a.exec();
}

---

this is my main.cpp code. This is the only page where I have written the code.

it says errors.

Quote:

---

error: invalid conversion from `char*' to `char'
error: `ui' was not declared in this scope
warning: unused variable 'ui'

---

I think you should start looking at the examples and tutorials that are part of the Qt installation to know more about signal & slots and UI development using Qt. Qt Assistant has every thing that you need to get started.

Code:

---

char DLLfunction()
{
    QLibrary myLib("dllprog");
    typedef char* (*MyPrototype)();
    MyPrototype myFunction =
    (MyPrototype) QLibrary::resolve("dllprog", "TestDll");
    char b = myFunction();
    return b;
}

---

there is something weird in your code as define MyPrototype as raturning char* and than you do:

Code:

---

char b = myFunction();

---

where you are assigning returned value to one char. Is it right?

a mistake.

the line now is

Code:

---

typedef char (*MyPrototype)();

---

I need a GUI application to display the contents of myFunction. I have a working console application.

Code:

---

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QLibrary>
#include <QLineEdit>
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindowClass)
{
 
      ui->setupUi(this);
 
QLibrary myLib("dllprog");
typedef char* (*MyPrototype)();
MyPrototype myFunction = (MyPrototype) QLibrary::resolve("dllprog", "TestDll");
 
char* b = myFunction();
ui->lineEdit->setText(b);
 
}
 
MainWindow::~MainWindow()
{
    delete ui;
}

---

This is my code display the characters that myFunction returns in a linedit.

I have created a pushButton and a lineEdit in the .ui file.

I am getting this error.

Quote:

---

:-1: error: collect2: ld returned 1 exit status

---

How can i solve this?

thanks for reading.