base operand of '->' has non-pointer type

Nils A

Hello, I'm using Qt Creator 3.5.1 (opensource), Based on Qt 5.5.1 (GCC 4.9.1 20140922, 64 bit), Built on Oct 13 2015 07:38:30

I try the Notepad code from "Getting Started Programming with Qt Widgets" from Qt at link http://doc.qt.io/qt-5/gettingstartedqt.html

In the fileopen dialogue is a part:
QTextStream in(&file);
ui->textEdit->setText(in.readAll());
file.close();

When I run this in the Qt ide (green arrow) I get the error:
error: base operand of '->' has non-pointer type 'Ui::NoteWindow'
ui->textEdit->setText(in.readAll());
.... ^
Since I'm new to Qt and especially Qt 5.5.1, I wonder what I do wrong? because I try to run an example I take from the Qt5 site itself.

Here the code from the example on Qt site:
http://doc.qt.io/qt-5/gettingstartedqt.html

void Notepad::on_actionOpen_triggered()
{
QString fileName = QFileDialog::getOpenFileName(this, tr("Open File"), QString(),
tr("Text Files (.txt);;C++ Files (.cpp *.h)"));

if (!fileName.isEmpty()) {
    QFile file(fileName);
    if (!file.open(QIODevice::ReadOnly)) {
        QMessageBox::critical(this, tr("Error"), tr("Could not open file"));
        return;
    }
    QTextStream in(&file);
    ui->textEdit->setText(in.readAll());
    file.close();
}

}

 Thanks in advance, Nils A

SGaist

Hi and welcome to devnet,

It means that it is not a pointer thus your notation is not correct. How did you declare it ?

Nils A

Hello Thanks,

Since I try the example from the site I did not declare the textEdit or the ui. This was done in / by the design mode of Qt5.

mrjj

hi
and you have the
notepad.ui
as part of the project?
also
in mainwindow.h
Do you have
...
private:
Ui::Notepad *ui;

Nils A

Yes I have absolutely. I follow all steps in the http://doc.qt.io/qt-5/gettingstartedqt.html link. That's why I'm a bit surprised with the error. I'm slow in reply because I can only reply every 500 seconds as a new user ... (As a new user, you can only post once every 500 second(s) until you have earned 2 reputation - please wait before posting again)

Nils A.

mrjj

can u check if u type
ui->
if it will suggest anything?
also, if u dblclick the UI it opens fine etc?
Also,
you do have
Ui::Notepad *ui; ?

Nils A

@mrjj Hello,

When I type ui it will give suggestions only after I type ::
If I choose ui::textEdit->setText(in.readAll()); I get an error,
Noteapp/notewindow.cpp:30: error: 'ui' is not a class or namespace
ui::textEdit->setText(in.readAll());
^

But, because this is an example application fron Qt on their site, why would they make it with errors? Do they test these apps?

Nils A.

Nils A

Here the files: noteapp.pro, notewindow.h and notewindow.ccp

// noteapp.pro
#-------------------------------------------------

Project created by QtCreator 2015-12-27T20:58:35

why is this so big??

#-------------------------------------------------

QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = Noteapp
TEMPLATE = app

SOURCES += main.cpp
notewindow.cpp

HEADERS += notewindow.h

FORMS += notewindow.ui

// notewindow.h
#ifndef NOTEWINDOW_H
#define NOTEWINDOW_H

#include "ui_notewindow.h"

class NoteWindow : public QMainWindow
{
Q_OBJECT

public:
explicit NoteWindow(QWidget *parent = 0);

private slots:
void on_quitButton_clicked();

void on_actionOpen_triggered();

void on_actionSave_triggered();

private:
Ui::NoteWindow ui;
};

#endif // NOTEWINDOW_H

// notewindow.ccp

#include "notewindow.h"
#include <QFileDialog>
#include <QFile>
#include <QMessageBox>
#include <QTextStream>

NoteWindow::NoteWindow(QWidget *parent) :
QMainWindow(parent)
{
ui.setupUi(this);
}

void NoteWindow::on_quitButton_clicked()
{
qApp->quit();
}

void NoteWindow::on_actionOpen_triggered()
{
QString fileName = QFileDialog::getOpenFileName(this, tr("Open File"), QString(),
tr("Text Files (.txt);;C++ Files (.cpp *.h)"));

  if (!fileName.isEmpty()) {
      QFile file(fileName);
      if (!file.open(QIODevice::ReadOnly)) {
          QMessageBox::critical(this, tr("Error"), tr("Could not open file"));
          return;
      }
      QTextStream in(&file);
      ui->textEdit->setText(in.readAll());
      file.close();

      //error: base operand of '->' has non-pointer type 'Ui::NoteWindow'
      //         ui->textEdit->setText(in.readAll());
      //             ^
  }

}

void NoteWindow::on_actionSave_triggered()
{
QString fileName = QFileDialog::getSaveFileName(this, tr("Save File"), QString(),
tr("Text Files (.txt);;C++ Files (.cpp *.h)"));

if (!fileName.isEmpty()) {
    QFile file(fileName);
    if (!file.open(QIODevice::WriteOnly)) {
        // error message
    } else {
        QTextStream stream(&file);
        stream << ui->textEdit->toPlainText();
        stream.flush();
        file.close();
    }
}

}

SGaist

ui is not a pointer so you should use ui.textEdit->toPlainText()

Nils A

Yes, that's it! You are great. Why would Qt make this mistake in their example code?

thanks,
Nils A.

SGaist

There's no mistake in the example, please read again the Notepad class. In the header they are declaring a pointer for ui and the initialization also shows they are allocating a new instance of Ui::Notepad in the constructor member initializer list

Nils A

Thanks again, but the example on the site really uses the -> and not a .

QTextStream in(&file);
ui->textEdit->setText(in.readAll());
file.close();

see http://doc.qt.io/qt-5/gettingstartedqt.html

SGaist

Yes, and again the example is correct.

Your code is a bit different: you have ui as Ui::Notepad ui;. In the example it's Ui::Notepad *ui;

Nils A

I see yes, but still strange (and an error) because the (in my case) NoteWindow class is created by the Qt-widget wizard. I did not type the code.

example code on the site;
#include <QMainWindow>

namespace Ui {
class Notepad;
}

class Notepad : public QMainWindow
{
Q_OBJECT

public:
explicit Notepad(QWidget *parent = 0);
~Notepad();

private:
Ui::Notepad *ui;
};

======
example created by the Qt-Wizard:

#ifndef NOTEWINDOW_H
#define NOTEWINDOW_H

#include "ui_notewindow.h"

class NoteWindow : public QMainWindow
{
Q_OBJECT

public:
explicit NoteWindow(QWidget *parent = 0);

private:
Ui::NoteWindow ui;
};

#endif // NOTEWINDOW_H

Nils A

@SGaist Thanks again Champ. You are right, there is no error in the example. The mixing of the example code (using the *) with the auto-generate code (not using the *) made my C++ virgin brain confused. But now I will never forget to check for *'s any more.
Have a good day! (now how to set this to solved?) (Ah, found this too. Solved!)